O(mn²)竟然过了。。。

#include <iostream>
#include <cstring>
#include <algorithm>
#include <queue>

using namespace std;

#define int long long
#define TRACE 1
#define tcout TRACE && cout
#define el printf("\n")
#define inf 0x7fffffff

int n, m;
int a[1010][1010];
int x1, x2, y1, y2; 

signed main()
{
    cin >> n >> m;
    while(m--){
        cin >> x1 >> y1 >> x2 >> y2;
        for(int i=x1; i<=x2; i++){
            for(int j=y1; j<=y2; j++){
                a[i][j]++;
            }
        }
    }
    for(int i=1; i<=n; i++){
        for(int j=1; j<=n; j++){
            cout << a[i][j] << ' ';
        }
        el;
    }
    return 0;
}

https://www.luogu.com.cn/record/100652450