#include <bits/stdc++.h>
using namespace std;
int main() {
    int t;
    scanf("%d", &t);
    while (t--) {
        int n, m;
        scanf("%d%d", &n, &m);
        if (m % (n - 1) == 0)
            printf("CSFNB!\n");
        else
            printf("%.6lf\n",
                   (ceil((double)m / (double)(n - 1)) - (double)m / (double)(n - 1)) * (double)(n - 2));
    }
    return 0;
}