UVA 350

#include<iostream>
#include <algorithm>
#include<vector>
using namespace std;
int main()
{
    int Z,I,M,L,flag=1;
    while(cin>>Z>>I>>M>>L)
    {
        if(Z==0&&I==0&&M==0&&L==0)break;
        int temp,temp2,i=0;
        temp=Z*L+I;
        vector<int>v;
        v.push_back(L);
        while(true)
        {
            temp2=temp%M;
            i++;
            vector<int>::iterator it;
            it=find(v.begin(),v.end(),temp2);
            if(it!=v.end())
            {
                cout<<"Case "<<flag<<": "<<i-(it-v.begin())<<endl;
                    break;
            }
            else
            {
                v.push_back(temp2);
                temp=Z*temp2+I;
            }
        }
        flag++;
    }
    return 0;
}