#include <bits/stdc++.h>
using namespace std;
#define LL long long
const int N = 1e5 + 10;
const int INF = 0x3f3f3f3f;
int a , b , c , d;
int main()
{
	cin >> a >> b >> c >> d;
	int gh = a + b + c;
	cout << gh % d;
	return 0;
}
//菜鸟驿站
//老六专属

sb