#include <bits/stdc++.h>

#define forn(i, n) for(int i = 0; i < int(n); i++)
 
using namespace std;

int main() {
	long long n, m;
	int a, b;
	
	cin >> n >> m >> a >> b;
	cout << min(n % m * b, (m - n % m) * a) << endl;
	return 0;
}

#include<bits/stdc++.h>

using namespace std;

const int N = 200 * 1000 + 555;
int n, k, a[N];

inline bool read() {
	if(!(cin >> n >> k))
		return false;
	for(int i = 0; i < n; i++)
		assert(scanf("%d", &a[i]) == 1);
	return true;
}

inline void solve() {
	sort(a, a + n);
	a[n++] = int(2e9);
	
	int ans = 0, u = 0;
	for(int i = 0; i < n - 1; i++) {
		while(u < n && a[i] == a[u])
			u++;
		if(a[u] - a[i] > k)
			ans++;
	}
	cout << ans << endl;
}

int main() {
#ifdef _DEBUG
	freopen("input.txt", "r", stdin);
	int tt = clock();
#endif

	if(read()) {
		solve();
#ifdef _DEBUG
		cerr << "TIME = " << clock() - tt << endl;
#endif
	}
	return 0;
}

#include <bits/stdc++.h>

using namespace std;

const int N = int(3e5) + 7;

int n;
string s[N];
char buf[N];
int cnt[N];

int getBalance(string &s){
	int bal = 0;
	for(int i = 0; i < s.size(); ++i){
		if(s[i] == '(')
			++bal;
		else
			--bal;
		
		if(bal < 0)
			return -1;
	}
	
	return bal;
}

string rev(string &s){
	string revs = s;
	reverse(revs.begin(), revs.end());
	for(int i = 0; i < revs.size(); ++i)
		if(revs[i] == '(')
			revs[i] = ')';
		else
			revs[i] = '(';
		
	return revs;
}

int main(){
	scanf("%d", &n);
	for(int i = 0; i < n; ++i){
		scanf("%s", buf);
		s[i] = buf;
	}

	for(int i = 0; i < n; ++i){
		int bal = getBalance(s[i]);
		if(bal != -1)
			++cnt[bal];
	}
	
	long long res = 0;	
	for(int i = 0; i < n; ++i){
		s[i] = rev(s[i]);
		int bal = getBalance(s[i]);
		if(bal != -1)
			res += cnt[bal];
	}
	
	printf("%I64d\n", res);
	return 0;
}

#include <bits/stdc++.h>

using namespace std;

const int N = int(1e3) + 7;

int n, a, b;
bool mat[N][N];

int main(){
	scanf("%d %d %d", &n, &a, &b);

	if(min(a, b) > 1){
		puts("NO");
		return 0;
	}
	
	if(a == 1 && b == 1){
		if(n == 2 || n == 3){
			puts("NO");
			return 0;
		}
		puts("YES");
		for(int i = 1; i < n; ++i)
			mat[i][i - 1] = mat[i - 1][i] = true;
		for(int i = 0; i < n; ++i){
			for(int j = 0; j < n; ++j)
				printf("%c", '0' + mat[i][j]);
			puts("");
		}
		return 0;
	}
	
	bool x = false;
	if(a == 1){
		swap(a, b);
		x = true;
	}
	for(int i = n - a; i > 0; --i)
		mat[i][i - 1] = mat[i - 1][i] = true;
	puts("YES");
	for(int i = 0; i < n; ++i){
			for(int j = 0; j < n; ++j)
				printf("%c", '0' + ((x ^ mat[i][j]) && (i != j)));
			puts("");
		}
	return 0;
}

#include <bits/stdc++.h>

#define forn(i, n) for (int i = 0; i < int(n); i++)

using namespace std;

const int INF = 1e9;
const long long INF64 = 1e18;
const int N = 1000 * 1000 + 13;

int n, m, k;
bool pos[N];
int lst[N], s[N], a[N];

int get(int l){
	int r = 0, i = -1, res = 0;
	while (r < n){
		if (lst[r] <= i)
			return INF;
		i = lst[r];
		r = lst[r] + l;
		++res;
	}
	return res;
}

int main() {
	scanf("%d%d%d", &n, &m, &k);
	forn(i, m) scanf("%d", &s[i]);
	forn(i, k) scanf("%d", &a[i]);
	forn(i, n) pos[i] = true;
	forn(i, m) pos[s[i]] = false;
	forn(i, n){
		if (pos[i])
			lst[i] = i;
		else if (i)
			lst[i] = lst[i - 1];
		else
			lst[i] = -1;
	}
	long long ans = INF64;
	forn(i, k){
		long long t = get(i + 1);
		if (t != INF)
			ans = min(ans, a[i] * t);
	}
	printf("%lld\n", ans == INF64 ? -1 : ans);
	return 0;
}

#include <bits/stdc++.h>

#define forn(i, n) for (int i = 0; i < int(n); i++)

using namespace std;

mt19937 rnd(time(NULL));

const int N = 1'000'013;

int n, m;
pair<int, int> e[N];
int a[N], rk[N];
long long sum[N], ans[N];

int p[N];

int getP(int a){
	return (a == p[a] ? a : p[a] = getP(p[a]));
}

bool merge(int a, int b){
	a = getP(a);
	b = getP(b);
	if (a == b) return false;
	if (rk[a] > rk[b]) swap(a, b);
	p[a] = b;
	rk[b] += rk[a];
	return true;
}

bool used[N];
vector<int> g[N];
int h[N];

void dfs(int v, int p){
	sum[v] = a[v];
	for (auto u : g[v]){
		if (u != p){
			h[u] = h[v] + 1;
			dfs(u, v);
			sum[v] += sum[u];
		}
	}
}

int main() {
	scanf("%d", &n);
	forn(i, n)
		scanf("%d", &a[i]);
	
	forn(i, n) p[i] = i, rk[i] = 1;
	scanf("%d", &m);
	forn(i, m){
		int &v = e[i].first;
		int &u = e[i].second;
		scanf("%d%d", &v, &u);
		--v, --u;
		if (merge(v, u)){
			g[v].push_back(u);
			g[u].push_back(v);
			used[i] = true;
		}
	}
	
	long long tot = 0;
	forn(i, n) tot += a[i];
	if (tot != 0){
		puts("Impossible");
		return 0;
	}
	
	dfs(0, -1);
	
	puts("Possible");
	forn(i, m){
		if (used[i]){
			int v = e[i].first, u = e[i].second;
			if (h[v] < h[u])
				ans[i] = sum[u];
			else
				ans[i] = -sum[v];
		}
		printf("%lld\n", ans[i]);
	}
	return 0;
}

#include<bits/stdc++.h>

using namespace std;

const int N = 200043;

int d[N];

void sieve()
{
	vector<int> pr;
 	for(int i = 2; i < N; i++) 
 	{
		if (d[i] == 0) 
		{
			d[i] = i;
			pr.push_back(i);
		}
		for(auto x : pr)
		{
			if (x > d[i] || x * 1ll * i >= N)
				break;
			d[i * x] = x;
		}
	}
}

int mobius(int x)
{
	int last = -1;
	int res = 1;
	while(x != 1)
	{
		if(last == d[x])
			res = 0;
		else
			res = -res;
		last = d[x];
		x /= d[x];
	}
	return res;
}

int mb[N];

vector<int> need_bfs[N];
int used[N];
vector<int> g[N];
int a[N];
int cc = 0;
int q[N];
int hd, tl;
int good[N];

int bfs(int x, int gc)
{
    hd = 0;
    tl = 0;
    q[tl++] = x;
    used[x] = cc;
    while(hd < tl)
    {
        int z = q[hd++];
        for(auto y : g[z])
        {
            if(good[a[y]] == cc && used[y] < cc)
            {
                used[y] = cc;
                q[tl++] = y;
            }
        }
    }
	return tl;
}

long long ans1[N];
long long ans2[N];

int main() {
	sieve();
	for(int i = 1; i < N; i++)
		mb[i] = mobius(i);
	int n;
	scanf("%d", &n);
	for(int i = 0; i < n; i++)
		scanf("%d", &a[i]);
	for(int i = 0; i < n - 1; i++)
	{
		int x, y;
		scanf("%d %d", &x, &y);
		--x;
		--y;
		g[x].push_back(y);
		g[y].push_back(x);
	}
	for(int i = 0; i < n; i++)
	{
		need_bfs[a[i]].push_back(i);
	}
	for(int i = 200000; i >= 1; i--)
	{
		cc++;
		for(int j = i; j <= 200000; j += i)
		    good[j] = cc;
		for(int j = i; j <= 200000; j += i)
		    for(auto x : need_bfs[j])
		    {
		        if(used[x] == cc) continue;
			    int z = bfs(x, i);
			    ans1[i] += z * 1ll * (z + 1) / 2;
		    }
	    for(int j = i, k = 1; j <= 200000; j += i, k++)
	        ans2[i] += mb[k] * ans1[j];
	}
	for(int i = 1; i <= 200000; i++)
		if(ans2[i])
			printf("%d %lld\n", i, ans2[i]);
	return 0;
}

#include<bits/stdc++.h>

using namespace std;

#define fore(i, l, r) for(int i = int(l); i < int(r); i++)

#define x first
#define y second

typedef long long li;
typedef long double ld;
typedef pair<int, int> pt;

template<class A, class B> ostream& operator <<(ostream &out, const pair<A, B> &p) {
	return out << "(" << p.x << ", " << p.y << ")";
}

template<class A> ostream& operator <<(ostream &out, const vector<A> &v) {
	out << "[";
	for(auto &e : v)
		out << e << ", ";
	return out << "]";
}

const int N = 1000 * 1000 + 555;
const int LOGN = 21;
int mind[N];
int pw[LOGN][N];

int n, a[N];
vector<int> g[N];
li res[N];

bool gen() {
	mt19937 rnd(42);
	n = 200 * 1000;
	fore(i, 0, n)
		a[i] = 831600;
	fore(i, 1, n) {
		int u = rnd() % i, v = i;
		g[u].push_back(v);
		g[v].push_back(u);
	}
	return true;
}

inline bool read() {
//	return gen();
	if(!(cin >> n))
		return false;
	fore(i, 0, n)
		assert(scanf("%d", &a[i]) == 1);
	fore(i, 0, n - 1) {
		int u, v;
		assert(scanf("%d%d", &u, &v) == 2);
		u--, v--;
		
		g[u].push_back(v);
		g[v].push_back(u);
	}
	return true;
}

vector<pt> dv[N];

inline int gcd(int a, int b) {
	int ans = 1;
	unsigned int u = 0, v = 0;
	while(u < dv[a].size() && v < dv[b].size()) {
		if(dv[a][u].x < dv[b][v].x)
			u++;
		else if(dv[a][u].x > dv[b][v].x)
			v++;
		else {
			ans *= pw[min(dv[a][u].y, dv[b][v].y)][dv[a][u].x];
			u++, v++;
		}
	}
	return ans;
}

bool used[N];
int sz[N];

void calcSz(int v, int p) {
	sz[v] = 1;
	for(int to : g[v]) {
		if(to == p || used[to])
			continue;
		calcSz(to, v);
		sz[v] += sz[to];
	}
}

int findC(int v, int p, int all) {
	for(int to : g[v]) {
		if(to == p || used[to])
			continue;
		if(sz[to] > all / 2)
			return findC(to, v, all);
	}
	return v;
}

int u[N], T = 0;
int cntD[N];

inline void addDiv(int d, int cnt) {
	if(u[d] != T)
		u[d] = T, cntD[d] = 0;
	cntD[d] += cnt;
}

int cds[N], szcds;

void calcDs(int v, int p, int gc) {
	gc = gcd(a[v], gc);
	cds[szcds++] = gc;
	for(int to : g[v]) {
		if(to == p || used[to])
			continue;
		calcDs(to, v, gc);
	}
}

vector<int> cps, cmx, vmx;

void check(int curd, int curg, int pos, int add) {
	if(pos >= (int)cps.size()) {
		if(u[curd] == T)
			res[curg] += cntD[curd] * 1ll * add;
		return;
	}
	
	fore(st, 0, cmx[pos] + 1) {
		check(curd, curg, pos + 1, add);
		
		curd *= cps[pos];
		if(st < vmx[pos])
			curg *= cps[pos];
	}
}

pt ops[N]; int szops;
int cntDiff[N];

void calc(int v) {
	calcSz(v, -1);
	int c = findC(v, -1, sz[v]);
	used[c] = 1;
	
//	cerr << "C = "<< c << endl;
	
	cps.resize(dv[a[c]].size());
	cmx.resize(cps.size());
	vmx.resize(cmx.size());
	
	fore(i, 0, cps.size()) {
		cps[i] = dv[a[c]][i].x;
		cmx[i] = dv[a[c]][i].y;
	}
	
	T++;
	addDiv(a[c], 1);
	
	for(int to : g[c]) {
		if(used[to]) continue;
		
		szcds = 0;
		calcDs(to, c, a[c]);
		fore(i, 0, szcds)
			cntDiff[cds[i]]++;
			
		szops = 0;
		fore(j, 0, szcds) {
			if(cntDiff[cds[j]] == 0)
				continue;
			
			int p = 0, val = cds[j];
			fore(i, 0, vmx.size()) {
				if(p >= (int)dv[val].size() || dv[val][p].x > cps[i])
					vmx[i] = 0;
				else
					vmx[i] = dv[val][p].y, p++;
			}
			
			check(1, 1, 0, cntDiff[cds[j]]);
			ops[szops++] = {cds[j], cntDiff[cds[j]]};
			cntDiff[cds[j]] = 0;
		}
		
		fore(j, 0, szops)
			addDiv(ops[j].x, ops[j].y);
	}
	
	for(int to : g[c]) {
		if(used[to]) continue;
		calc(to);
	}
}

inline void solve() {
	iota(mind, mind + N, 0);
	fore(i, 2, N) {
		if(mind[i] != i)
			continue;
		
		pw[0][i] = 1;
		fore(st, 1, LOGN)
			pw[st][i] = pw[st - 1][i] * i;
		
		for(li j = i * 1ll * i; j < N; j += i)
			mind[j] = min(mind[j], i);
	}
	fore(i, 2, N) {
		int val = i;
		while(mind[val] > 1) {
			if(dv[i].empty() || dv[i].back().x != mind[val])
				dv[i].emplace_back(mind[val], 0);
			dv[i].back().y++;
			val /= mind[val];
		}
	}
	
	memset(res, 0, sizeof res);
	
	T = 0;
	calc(0);
	
	fore(i, 0, n)
		res[a[i]]++;
	
	fore(i, 1, 1000'000 + 1) {
		if(res[i])
			printf("%d %lld\n", i, res[i]);
	}
}

int main() {
#ifdef _DEBUG
	freopen("input.txt", "r", stdin);
	int tt = clock();
#endif

	if(read()) {
		solve();
#ifdef _DEBUG
		cerr << "TIME = " << clock() - tt << endl;
#endif
	}
	return 0;
}