#include <iostream>
using namespace std;
int C(int A, int B, int K, int x){
while (K>0){
x=abs(A*x + B);
K--;
}
return x;
}
int main()
{
int D, a, k, x;
cin>>D>>a>>k>>x;
cout<<C(D, a, k, x);
}
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