求助，Unknown Error

#include <iostream>
#include <cmath>
#include <cstring>
#include <string>
#include <set>
#include <algorithm>
#define ll long long
#define INF 0x3f3f3f3f
using namespace std;
char g[10][10];
int vis[10][10];
int n = 4;
int flag = 0;
void dfs(int x, int y) {
	if(x > 4 || y > 4 || x < 1 || y < 1)
		return;
	if(y <= 2 && (g[x][y+1] == 'x' && g[x][y+2] == 'x') || 
	   (g[x][y+1] == 'x' && g[x][y+2] == '.') || 
	   (g[x][y+1] == '.' && g[x][y+2] == 'x'))
	   	flag = 1;
	if(y >= 3 && (g[x][y-1] == 'x' && g[x][y-2] == 'x') || 
	   (g[x][y-1] == 'x' && g[x][y-2] == '.') || 
	   (g[x][y-1] == '.' && g[x][y-2] == 'x'))
	   	flag = 1; 
	if(x <= 2 && (g[x+1][y] == 'x' && g[x+2][y] == 'x') || 
	   (g[x+1][y] == 'x' && g[x+2][y] == '.') || 
	   (g[x+1][y] == '.' && g[x+2][y] == 'x'))
	   	flag = 1;
	if(x >= 3 && (g[x-1][y] == 'x' && g[x-2][y] == 'x') || 
	   (g[x-1][y] == 'x' && g[x-2][y] == '.') || 
	   (g[x-1][y] == '.' && g[x-2][y] == 'x'))
	   	flag = 1;
	//对角线 
	if(x <= 2 && y <= 2 && (g[x+1][y+1] == 'x' && g[x+2][y+2] == 'x') || 
	   (g[x+1][y+1] == 'x' && g[x+2][y+2] == '.') || 
	   (g[x+1][y+1] == '.' && g[x+2][y+2] == 'x'))
	   	flag = 1; 
	if(x >= 3 && y >= 3 && (g[x-1][y-1] == 'x' && g[x-2][y-2] == 'x') || 
	   (g[x-1][y-1] == 'x' && g[x-2][y-2] == '.') || 
	   (g[x-1][y-1] == '.' && g[x-2][y-2] == 'x'))
	   	flag = 1; 
	if(x <= 2 && y >= 3 && (g[x+1][y-1] == 'x' && g[x+2][y-2] == 'x') ||
	   (g[x+1][y-1] == 'x' && g[x+2][y-2] == '.') || 
	   (g[x+1][y-1] == '.' && g[x+2][y-2] == 'x'))
	   	flag = 1;
}
int main() {
	ios::sync_with_stdio(false);  cin.tie(0);
	for(int i = 1; i <= n; ++i) {
		for(int j = 1; j <= n; ++j) {
			cin >> g[i][j];
		}
	} 
	for(int i = 1; i <= n; ++i) {
		for(int j = 1; j <= n; ++j) {
			if(g[i][j] == 'x')
				dfs(i,j);
			if(flag) {
				cout << "YES";
				return 0;
			}
		}
	}
	cout << "NO"; 
	return 0;
}