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