#include <iostream>
#include <string>
#include <sstream>

using namespace std;

class solution {
public:
    long double res(int n, int m) {
        if (m % (n - 1) == 0)  //∏’∫√’˚≥˝
            return -1.0;

        double f = m / (n - 1 + 0.0);  //◊‘º∫“—æ≠÷ß∏∂µƒ«Æ
        double fuli = m - (n - 2) * (m / (n - 1) + 1);
        fuli = f - fuli;
        return fuli;
    }
};

int main() {
    int n;
    cin >> n;
    solution a;
    for (int i = 0; i < n; i++) {
        int people, money;
        cin >> people >> money;
        double f = a.res(people, money);
        string temp;
        if (f > 0) {
            printf("%.6f\n", f);
        } else
            printf("CSFNB!\n");
    }
    return 0;
}

/sandbox/1/a.cpp: In function 'int main()':
/sandbox/1/a.cpp:36:4: error: 'printf' was not declared in this scope
    printf("%.6f\n",f);
    ^~~~~~
/sandbox/1/a.cpp:36:4: note: 'printf' is defined in header '<cstdio>'; did you forget to '#include <cstdio>'?
/sandbox/1/a.cpp:4:1:
+#include <cstdio>
 
/sandbox/1/a.cpp:36:4:
    printf("%.6f\n",f);
    ^~~~~~
/sandbox/1/a.cpp:39:4: error: 'printf' was not declared in this scope
    printf("CSFNB!\n");
    ^~~~~~
/sandbox/1/a.cpp:39:4: note: 'printf' is defined in header '<cstdio>'; did you forget to '#include <cstdio>'?