#include <iostream>

using namespace std;


int main(){

	int A,B,C,D;
	int moda,modb,modc;
	long ans = 0;

	cin >> A;
	cin >> B;
	cin >> C;
	cin >> D;
	moda = A % D;
	modb = B % D;
	modc = C % D;
	ans = (moda + modb + modc) % D;
	cout << ans << endl;	

	return 0;
}