样例过了，却全WAqwq

#include <bits/stdc++.h>
#define init ios::sync_with_stdio(false), cin.tie(0), cout.tie(0)
#define MX 500
using namespace std;

typedef long long ll;

ll n, m, q[MX*MX+1], q1[MX*MX+1], a[MX+1][MX+1], v[MX+1][MX+1], h, t, ans;
ll dx[4] = {1, 0, 0, -1}, dy[4] = {0, 1, -1, 0};
bool flag;

void __init__() {
	init;
	cin >> n >> m;
	for (ll i = 1; i <= n; i++)  {
		for (ll j = 1; j <= m; j++) {
			char x;
			cin >> x;
			if (x == '0')
				a[i][j] = 0;
			else
				a[i][j] = 1;
		}
	}
	return ;
}

void bfs(int x, int y) {
	t++;
	q[t] = x;
	q1[t] = y;
	v[x][y] = 1;
	if(!a[x][y]) a[x][y] = 2;
	while (h < t) {
		h++;
		for (ll i = 0; i < 4; i++) {
			ll xa = q[h]+dx[i], ya = q1[h]+dy[i];
			if (xa>-1 && ya>-1 && xa<=n+1 && ya<=m+1 && !v[xa][ya] && !a[xa][ya]) {
				t++;
				q[t] = xa;
				q1[t] = ya;
				v[xa][ya] = 1;
				a[xa][ya] = 2;
				bfs(xa, ya);
			}
		}
	}
}

int main() {
	__init__();
	bfs(0, 0);
	for (ll i = 1; i <= n; i++)
		for (ll j = 1; j <= m; j++)
			if (!a[i][j]) ans++;
	cout << ans;
	return 0;
}