#include <iostream>
using namespace std;
long long t;
double n;
double m;
int main() {
    cin >> n;
    for (int i = 0; i < n; i++) {
        cin >> n >> m;
        n--;
        double ans = (int)m % (int)n == 0 ? 0 : ((int)(m / n + 1) * (n - 1) + m / n - m);
        if (ans == 0) {
            cout << "CSFNB!\n";
        } else
            cout << ans << '\n';
    }
    return 0;
}