#include <iostream>
using namespace std;
typedef long long ll;
int main(){
  ll a,b,c,d,x;
  cin>>a>>b>>c>>d;
  a%=d;
  b%=d;
  c%=d;
  x=a+b+c;
  x%=d;
  cout<<x<<endl;
  return 0;
}