#include <stdio.h>

int main(void)
{
	unsigned long a, b, c, d;
	unsigned long ans;

	scanf("%lu %lu %lu %lu", &a, &b, &c, &d);
	
	ans = ((a % d) + (b % d) + (c % d)) % d;

	printf("%lu\n", ans);

	return 0;
}