样例输出36求助

#include <bits/stdc++.h>
#define int long long
using namespace std;
const int N = 22;
int h,w,ax,ay,ans,dx[4] = {1,0,-1,0},dy[4] = {0,1,0,-1};
bool flag[N][N];
char mig[N][N];
void dfs(int x,int y) {
	//ans = max(ans,s);
	//ans++;
	//	cout << x << " " << y << " " << ans << endl;
	//flag[x][y] = 1;
	for(int i = 0;i < 4;i++) {
		int xx = x + dx[i],yy = y + dy[i];
		if(mig[xx][yy] == '.' && !flag[xx][yy] && xx <= h && yy <= w && xx > 0 && yy > 0) {
			ans++;
			flag[xx][yy] = 1;
			dfs(xx, yy); 
		}
	}
}
signed main() {
	//freopen("test.in","r",stdin);
	//freopen("test.out","w",stdout);
	cin >> h >> w;
	//cout << 114514;
	for(int i = 1;i <= h;i++) {
		for(int j = 1;j <= w;j++) {
			//cout << 114514;
			cin >> mig[i][j];
			if(mig[i][j] == '@'){
				ax = i, ay = j;
			}		
		}
	}
	dfs(ax,ay);
	cout << ans + 1;
}