#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define int long long

signed main(void) {
  ll a,b,c,d;
  cin>>a>>b>>c>>d;
  ll ans=a%d;
  ans*=b;
  ans%=d;
  ans*=c;
  ans%=d;
  cout<<ans<<endl;
  return 0;
}