#include <bits/stdc++.h>

using namespace std;

const int maxn = 1e5 + 5;

int n, L, a;
int t[maxn], l[maxn];

int main(){
	scanf("%d%d%d", &n, &L, &a);
	for(int i = 0; i < n; i++){
		scanf("%d%d", &t[i], &l[i]);
	}
	int start = 0;
	int ans = 0;
	for(int i = 0; i < n; i++){
		ans += (t[i] - start)/a;
		start = t[i] + l[i];
	}
	ans += (L - start)/a;
	printf("%d", ans);
	return 0;
}

#include<bits/stdc++.h>

using namespace std;

const int maxn = (int)1e3 + 3;

int n, m;
char a[maxn][maxn];
bool can[maxn][maxn];
vector<int> must_have[maxn][maxn];

inline bool inside(int x, int y){
	return x >= 0 && y >= 0 && x < n && y < m;
}

int main(){
	scanf("%d%d", &n, &m);
	for(int i = 0; i < n; i++)
		for(int j = 0; j < m; j++)
			can[i][j] = true;
	for(int i = 0; i < n; i++)
		for(int j = 0; j < m; j++){
			do{
				a[i][j] = getc(stdin);
			}while(a[i][j] != '.' && a[i][j] != '#');
			for(int dx = -1; dx <= 1; dx++)
				for(int dy = -1; dy <= 1; dy++){
					if(abs(dx) + abs(dy) == 0 || !inside(i + dx, j + dy))continue;
					if(a[i][j] == '.')can[i + dx][j + dy] = false;
					else if (i + dx != 0 && j + dy != 0 && i + dx != n - 1 && j + dy != m - 1)must_have[i][j].push_back((i + dx) * m + j + dy);
				}
		}
	for(int i = 0; i < n; i++)
		for(int j = 0; j < m; j++){
			bool good = false;
			if(a[i][j] == '.')continue;
			for(int cand : must_have[i][j]){
				int x = cand/m, y = cand%m;
				good |= can[x][y];
			}
			if(!good){printf("NO"); return 0;}
		}
	printf("YES");
	return 0;
}

#include <bits/stdc++.h>

using namespace std;

const int maxn = 1e6 + 6;

int seq[maxn];
int ans[maxn];
int ptr = 0;

void solve(int n, int mul){
	if(n == 1){ans[ptr++] = mul; return;}
	if(n == 2){ans[ptr++] = mul; ans[ptr++] = mul * 2; return;}
	if(n == 3){ans[ptr++] = mul; ans[ptr++] = mul; ans[ptr++] = mul * 3; return;}
	for(int i = 0; i < n; i++)if(seq[i]&1)ans[ptr++] = mul;
	for(int i = 0; i < n/2; i++)seq[i] = seq[2*i + 1]/2;
	solve(n/2, mul * 2);
}

int main(){
	int n;
	scanf("%d", &n);
	for(int i = 0; i < n; i++)seq[i] = i + 1;
	solve(n, 1);
	for(int i = 0; i < n; i++)printf("%d ", ans[i]);
	return 0;
}

#include<bits/stdc++.h>

using namespace std;

typedef long double dbl;

const dbl eps = 1e-9;

inline bool gt(const dbl & x, const dbl & y){
	return x > y + eps;
}

inline bool lt(const dbl & x, const dbl & y){
	return y > x + eps;
}

inline dbl safe_sqrt(const dbl & D){
	return D < 0 ? 0 : sqrt(D);
}

struct pt{
	dbl x, y;
	pt(){}
	pt(dbl a, dbl b):x(a), y(b){}
};


const int N = 1e5 + 5;
const int STEPS = 150;

int n;
pt p[N];

inline bool can(dbl R){
	dbl l = -1e16 - 1, r = 1e16 + 1;
	for(int i = 0; i < n; i++){
		dbl b = -2 * p[i].x;
		dbl c = p[i].x * p[i].x + p[i].y * p[i].y - 2 * p[i].y * R;
		dbl D = b * b - 4 * c;
		if(lt(D, 0))
			return false;
		D = safe_sqrt(D);
		dbl x1 = p[i].x - D/2, x2 = p[i].x + D/2;
		l = max(l, x1);
		r = min(r, x2);
	}
	return !gt(l, r);
}

int main(){
	ios_base::sync_with_stdio(false);
	cin.tie(0);
	cin >> n;
	bool has_positive = false, has_negative = false;
	for(int i = 0; i < n; i++){
		int x, y;
		cin >> x >> y;
		p[i] = pt(x, y);
		if(y > 0)has_positive = true;
		else has_negative = true;
	}
	if(has_positive && has_negative){
		cout << -1 << endl;
		return 0;
	}
	if(has_negative){
		for(int i = 0; i < n; i++)
			p[i].y = -p[i].y;
	}
	dbl L = 0, R = 1e16;
	std::function<dbl(dbl, dbl)> get_mid;
	if(can(1)){
		R = 1;
		get_mid = [](dbl l, dbl r){return (l + r)/2.0;};
	}
	else{
		L = 1;
		get_mid = [](dbl l, dbl r){return sqrt(l * r);};
	}
	for(int step = 0; step < STEPS; step++){
		dbl mid = get_mid(L, R);
		if(can(mid))
			R = mid;
		else
			L = mid;
	}
	cout.precision(16);
	cout << fixed << get_mid(L, R) << endl;
}

#include<bits/stdc++.h>

using namespace std;

typedef long long ll;

const int maxn = 1e5 + 5;
const int lg = 20;
const ll inf = 1e18;

int n, L;
ll S;
ll t[4 * maxn];
ll t_add[4 * maxn];
int cid = 0;
int w[maxn];
vector<int> down[maxn];
ll sum[maxn];
int up[maxn];
int p[maxn][lg];
ll dp[maxn];
int id[maxn], rb[maxn];
ll dp_sum[maxn];
vector<int> rm[maxn];

inline ll get_sum(int v){
	return v == -1 ? 0 : sum[v];
}

void preprocess(int v, int pr = -1){
	sum[v] = get_sum(pr) + w[v];
	p[v][0] = pr;
	up[v] = v;
	id[v] = rb[v] = cid++;
	for(int i = 1; i < lg; i++)
		p[v][i] = p[v][i - 1] == -1 ? -1 : p[p[v][i - 1]][i - 1];
	int dist = L - 1;
	for(int i = lg - 1; i >= 0; i--){
		if(p[up[v]][i] == -1 || (1<<i) > dist)continue;
		if(get_sum(v) - get_sum(p[up[v]][i]) + w[p[up[v]][i]] <= S){
			dist -= 1<<i;
			up[v] = p[up[v]][i];
		}
	}
	rm[up[v]].push_back(v);
	for(int u : down[v]){
		preprocess(u, v);
		rb[v] = max(rb[v], rb[u]);
	}
}

inline void push(int v){
	t[2*v] += t_add[v];
	t[2*v + 1] += t_add[v];
	t_add[2*v] += t_add[v];
	t_add[2*v + 1] += t_add[v];
	t_add[v] = 0;
}

void build_tree(int v, int l, int r){
	t[v] = inf;
	if(l == r)
		return;
	int mid = (l + r)/2;
	build_tree(2*v, l, mid);
	build_tree(2*v + 1, mid + 1, r);
}

ll get_tree(int v, int l, int r, int ul, int ur){
	if(ul > ur)
		return inf;
	if(l == ul && r == ur)
		return t[v];
	push(v);
	int mid = (l + r)/2;
	return min(get_tree(2*v, l, mid, ul, min(ur, mid)), get_tree(2*v + 1, mid + 1, r, max(ul, mid + 1), ur));
}

void set_tree(int v, int l, int r, int pos, ll val){
	if(l == r){
		t[v] = val;
		return;
	}
	push(v);
	int mid = (l + r)/2;
	if(pos <= mid)
		set_tree(2*v, l, mid, pos, val);
	else
		set_tree(2*v + 1, mid + 1, r, pos, val);
	t[v] = min(t[2*v], t[2*v + 1]);
}

void add_tree(int v, int l, int r, int ul, int ur, ll val){
	if(ul > ur)return;
	if(l == ul && r == ur){
		t[v] += val;
		t_add[v] += val;
		return;
	}
	push(v);
	int mid = (l + r)/2;
	add_tree(2*v, l, mid, ul, min(ur, mid), val);
	add_tree(2*v + 1, mid + 1, r, max(ul, mid + 1), ur, val);
	t[v] = min(t[2*v], t[2*v + 1]);
}

inline void upd(int v){
	dp[v] = 1 + get_tree(1, 0, n - 1, id[v], rb[v]);
}

inline void add(int v){
	set_tree(1, 0, n - 1, id[v], 0);
	add_tree(1, 0, n - 1, id[v], rb[v], dp_sum[v] - dp[v]);
}

inline void remove(int v){
	set_tree(1, 0, n - 1, id[v], inf);
}

void solve(int v){
	for(int u : down[v]){
		solve(u);
		dp_sum[v] += dp[u];
	}
	add(v);
	dp[v] = maxn;
	upd(v);
	add_tree(1, 0, n - 1, id[v], rb[v], -dp[v]);
	for(int u : rm[v])
		remove(u);
}

int main(){
	scanf("%d%d%lld", &n, &L, &S);
	for(int i = 0; i < n; i++){
		scanf("%d", &w[i]);
		if(w[i] > S){printf("-1"); return 0;}
	}
	for(int i = 1; i < n; i++){
		int j;
		scanf("%d", &j);
		down[--j].push_back(i);
	}
	preprocess(0);
	build_tree(1, 0, n - 1);
	solve(0);
	printf("%lld", dp[0]);
}

#include<bits/stdc++.h>

using namespace std;

typedef long long ll;

const int maxn = 1e5 + 5;
const int lg = 20;
const ll inf = 1e18;

int n, L;
ll S;
int w[maxn];
vector<int> down[maxn];
ll sum[maxn];
int up[maxn];
int h[maxn];
int p[maxn][lg];
int path[maxn];

inline ll get_sum(int v){
	return v == -1 ? 0 : sum[v];
}

void preprocess(int v, int pr = -1){
	sum[v] = get_sum(pr) + w[v];
	p[v][0] = pr;
	h[v] = pr == -1 ? 0 : (1 + h[pr]);
	up[v] = v;
	for(int i = 1; i < lg; i++)
		p[v][i] = p[v][i - 1] == -1 ? -1 : p[p[v][i - 1]][i - 1];
	int dist = L - 1;
	for(int i = lg - 1; i >= 0; i--){
		if(p[up[v]][i] == -1 || (1<<i) > dist)continue;
		if(get_sum(v) - get_sum(p[up[v]][i]) + w[p[up[v]][i]] <= S){
			dist -= 1<<i;
			up[v] = p[up[v]][i];
		}
	}
	for(int u : down[v]){
		preprocess(u, v);
	}
}

int solve(int v){
	int ans = 0;
	int best = -1;
	for(int u : down[v]){
		ans += solve(u);
		if(path[u] == u)continue;
		if(best == -1 || h[best] > h[path[u]])
			best = path[u];
	}
	if(best == -1){
		best = up[v];
		++ans;
	}
	path[v] = best;
	return ans;
}

int main(){
	scanf("%d%d%lld", &n, &L, &S);
	for(int i = 0; i < n; i++){
		scanf("%d", &w[i]);
		if(w[i] > S){printf("-1"); return 0;}
	}
	for(int i = 1; i < n; i++){
		int j;
		scanf("%d", &j);
		down[--j].push_back(i);
	}
	preprocess(0);
	printf("%d", solve(0));
}