UVA350-水题

#include<iostream>

using namespace std;

int main()
{
	int c = 0;
	int Z, L, I, M;
	while (cin >> Z >> I >> M >> L)
	{
		c++;
		if(Z == L && L == I && I == M && M == 0)
		{
			return 0;
		}
		int i = 1;
		int K, P;
		I = I % M;
		Z = Z % M;
		K = L;
		L = P = (Z * L + I) % M;
		while (K != L)
		{
			L = (Z * L + I) % M;
			if(L == P)
				break;
			i++;
		}
		cout << "Case " << c << ": " << i << endl;
	}
	return 0;
}