I want to restart CP after more than 2 years

Can you guys help me,

Things to know before restarting

getting wrong answer

problem

[my code]

#include <bits/stdc++.h>
#define ll long long int
#define rep(i, a, n) for (ll i = a; i < n; i++)
#define ff first
#define ss second
#define endl '\n'

using namespace std;
void solve() {
	ll n, m; cin >> n >> m;
	ll g[n][m];
	ll x, y, mx = 0;
	queue<pair<ll, ll>>q;
	ll vis[n][m];
	rep(i, 0, n) {
		rep(j, 0, m) {
			cin >> g[i][j];
			vis[i][j] = 0;
			mx = max(mx, g[i][j]);
		}
	}
	rep(i, 0, n) {
		rep(j, 0, m) {
			if (g[i][j] == mx) { vis[i][j] = 1; q.push({i, j});}
		}
	}

	ll xx[4] = { -1, 0, 1, 0};
	ll yy[4] = {0, 1, 0, -1};

	ll ans = 0;
	while (!q.empty()) {
		x = q.front().ff;
		y = q.front().ss;
		q.pop();
		rep(i, 0, 4) {
			ll X = x + xx[i];
			ll Y = y + yy[i];
			if (X < 0 or Y <0 or Y > m - 1 or X > n - 1) continue;

			if (!vis[X][Y]) {
				if (g[X][Y] == g[x][y]) continue;
				else {
					if ((g[x][y] - g[X][Y]) == 1) {
						q.push({X, Y});
						vis[X][Y] = 1;
					}
					else if ((g[x][y] - g[X][Y]) > 1) {
						vis[X][Y] = 1;
						ans += (g[x][y] - g[X][Y]) - 1;
						g[X][Y] = g[x][y] - 1;
						q.push({X, Y});
					}
				}
			}
		}
	}
	cout << ans << endl;
}

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);
	ll t;
	cin >> t;
	rep(i, 1, t + 1)
	{
		cout << "Case #" << i << ": ";
		solve();
	}
	return 0;
}