Hambar

#include <bits/stdc++.h>
using namespace std;

short n, m, a[1002][1002];

int main(){
    ifstream cin("hambar.in");
    ofstream cout("hambar.out");
    cin >> n >> m;
    vector<vector<bool> > v(n + 1, vector<bool>(n + 1, 1));
    while(m--){
        short x, y;
        cin >> x >> y;
        v[x][y] = 0;
    }
    for(short j = 1; j <= n; ++j){
        for(short i = 1; i <= n; ++i)
            a[i][j] = a[i - 1][j] + v[i][j];
    }
    short ans = 0, s = 0, set = 0;
    for(short r1 = 1; r1 <= n; ++r1){
        for(short r2 = r1; r2 <= n; ++r2){
            s = 0, set = r2 - r1 + 1;
            for(short j = 1; j <= n; ++j){

                if(a[r2][j] - a[r1 - 1][j] == set)
                    s += set;
                else
                    s = 0;
                ans = max(ans, s);

            }
        }
    }
    cout << ans << '\n';
    cin.close(), cout.close();
}