#pragma GCC optimize(3, "Ofast", "inline")
#include <bits/stdc++.h>
#define int long long
#define x first
#define y second
#define debug(x) cout << #x " = " << x << '\n';
using namespace std;

void solve() {
    int n, m;
    cin >> n >> m;
    if (m % (n - 1) == 0)
        cout << "CSFNB!" << '\n';
    else
        cout << fixed << setprecision(6) << ceil(m * 1.0 / (n - 1)) * (n - 2) + (m * 1.0 / (n - 1)) - m
             << '\n';
}

signed main() {
    // freopen("Sample.in", "r", stdin);
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    int T = 1;
    cin >> T;
    while (T--) solve();
    return 0;
}