#include <bits/stdc++.h>

using namespace std;

int main() {
    ios::sync_with_stdio(false); //读入输出优化的强迫症
    int n, m;
    int num = 0;
    //设置输出为小数点后5位
    cout << fixed << setprecision(5);
    while (true) {
        cin >> n >> m;
        num++;
        if (n == 0 && m == 0) break;
        double sum = 0.0;
        for (int i = n; i <= m; i++) {
            sum += 1 / pow(i, 2);
        }
        cout << "Case "<<num<<":"<<sum << endl;
    }
    return 0;
}