bool check(int n, int i) {
    long long left = 0, right = 0;
    for (int k = 0; k <= i; k++) left += (long long)(n + k) * (n + k);
    for (int k = i + 1; k <= 2 * i; k++) right += (long long)(n + k) * (n + k);
    return left == right;
}