#include <iostream>
#include <math.h>
using namespace std;

int main() {
    int i;
    cin >> i;
    int j[i], k[i];
    double float w[i];
    for (int n = 0; n < i; n++) {
        cin >> j[n] >> k[n];
        j[n]--;
        w[n] = ((ceil((double)k[n] / j[n]) - (double)k[n] / j[n])) * (j[n] - 1);
    }
    for (int n = 0; n < i; n++) {
        if (w[n] <= 0) {
            cout << "CSFNB!" << endl;
        } else {
            printf("%.6f\n", w[n]);
        }
    }

    return 0;
}

/sandbox/1/a.cpp: In function 'int main()':
/sandbox/1/a.cpp:10:5: error: two or more data types in declaration of 'w'
   10 |     double float w[i];
      |     ^~~~~~
/sandbox/1/a.cpp:15:9: error: 'w' was not declared in this scope
   15 |         w[n] = ((ceil((double)k[n] / j[n]) - (double)k[n] / j[n])) * (j[n] - 1);
      |         ^
/sandbox/1/a.cpp:19:13: error: 'w' was not declared in this scope
   19 |         if (w[n] <= 0)
      |             ^