#include <iostream>
using namespace std;
int cmmdc (int a, int b) {
    if (a > b) {
        return cmmdc(a - b, b);
    }
    if (a < b) {
        return cmmdc(a, b - a);
    }
    if (a == b) {
        return a;
    }
}
int toPrime(int a) {
    for (int i = 1; i <= a / 2 ; ++i) {
        if (a % i == 0) {
            if (a / i == 1) {
                return a;
            }
            else {
                a = a / i;
            }
        }
    }
    return a;
}
int main() {
    float N, M;
    cin >> N >> M;
    int count = 0, steps;
    while (N != 0 && M != 0) {
        count++;
        if (cmmdc(N, M) != 1) {
            steps = (M - N) / toPrime(M - N);
        }
        else {
            steps = -1;
        }
        cout << "Case " << count << ": " << steps;
        cin >> N >> M;
    }
}