it seems that there's a potential issue that could lead to a segmentation fault. This can occur if the values of i and j in your queries go out of bounds of the array a.

You might want to include some checks to ensure that i and j are within the valid range before accessing a[i][j]. Here's an updated version of your code that includes these checks:

include

using namespace std;

int main() { long long i, j, x, n, q, k, a[10000][10000];

cin >> n >> q; // read the number of lines and queries

// save the arrays as a matrix
for (i = 0; i < n; i++) {
    cin >> k; // read the number of columns
    for (j = 0; j < k; j++) {
        cin >> a[i][j]; // read the value
    }
}

// solve the queries
for (x = 0; x < q; x++) {
    cin >> i >> j; // read the position of the wanted value

    if (i >= 0 && i < n && j >= 0 && j < k) {
        cout << a[i][j] << endl; // write the found value
    } else {
        cout << "Invalid query!" << endl;
    }
}

return 0;

} This code includes a check to ensure that i is within the range of [0, n) and j is within the range of [0, k) before accessing a[i][j]. This should help prevent potential segmentation faults caused by accessing elements outside the array bounds.