#include <stdio.h>
#include <algorithm>
#include <iostream>
#include <string>
#include <vector>
#include <functional>
#include <map>
#include <iomanip>
#include <math.h> 
#include <stack>
#include <queue>
#include <bitset>
#include <cstdlib>
#include <tuple>
#include <cctype>
#include <ctype.h>
#include <set>
#include <sstream>

using namespace std;

int main(){
	int i, j;
	long a, b, c, d;

	cin >> a >> b >> c >> d;


	a %= d;
	b %= d;
	c %= d;

	long ans = 0;

	if (a + b + c >= d) {
		ans = (a + b + c) % d;
	}
	else {
		ans = a + b + c;
	}

	cout << ans << endl;





	getchar();
	getchar();
	return 0;
}