max_matrix_with_1

#include <iostream>
#include <vector>
#include <string>
using namespace std;
bool if_ones(int i0, int j0, int size, vector<int>& mas) {
    int n = sqrt(mas.size());
    for (int i = i0; i < i0 + size; ++i) {
        for (int j = j0; j < j0 + size; ++j) {
            if (mas[i * n + j] != 1) {
                return false;
            }
        }
    }
    return true;
}
int main() {
    int n;
    cin >> n;
    vector<int> mas(n * n);
    for (int i = 0; i < n; ++i) {
        for (int j = 0; j < n; ++j) {
            int el;
            cin >> el;
            mas[i * n + j] = el;
        }
    }
    int size = n;
    for (int k = n; k >= 1; --k) {
        for (int i = 0; i < n - k + 1; ++i) {
            for (int j = 0; j < n - k + 1; ++j) {
                if (if_ones(i, j, k, mas)) {
                    cout << size << endl;
                    system("pause");
                    return 0;
                }
            }
        }
        --size;
    }
    cout << size << endl;
    system("pause");
    return 0;
}