求助大佬，为什么会re，不知道问题出在哪里

#include <iostream>
using namespace std;

int a[201];     //一行中的每个数

int main() {
    int n;
    cin >> n;
    int sum = 0;
    for (int i = 1; i <= n * n; i++) {
        cin >> a[i];
        if (i % 2 != 0) {
            for (int j = 1; j <= a[i]; j++) {
                cout << 0; sum++; if (sum % n == 0) cout << "\n";
            }
        }
        else {
            for (int k = 1; k <= a[i]; k++) {
                sum++; cout << 1; if (sum % n == 0) cout << "\n";
            }
        }
    }
    return 0;
}