#include <stdio.h>

int main()
{
	int p, q, r;
	long long K;
	scanf("%d %d %d %lld", &p, &q, &r, &K);
	p %= 10;
	q %= 10;
	r %= 10;

	int i, s, flag[1000] = {};
	flag[p * 100 + q * 10 + r] = 1;
	for (i = 2; 1; i++) {
		s = (p + q + r) % 10;
		p = q;
		q = r;
		r = s;
		s = p * 100 + q * 10 + r;
		if (flag[s] > 0) break;
		else flag[s] = i;
	}
	
	if (K < i) {
		for (s = 0; s < 1000; s++) if (flag[s] == K) break;
		printf("%d\n", s / 100);
	} else {
		K = (K - flag[s]) % (i - flag[s]);
		p = s / 100;
		q = s / 10 % 10;
		r = s % 10;
		while (K > 0) {
			s = (p + q + r) % 10;
			p = q;
			q = r;
			r = s;
			K--;
		}
		printf("%d\n", p);
	}
	fflush(stdout);
	return 0;
}