#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <iomanip>
#include <cmath>
#include <stdio.h>
#include <queue>
#include <deque>
#include <cstdio>
#include <set>
#include <map>
#include <bitset>
#include <stack>
#include <cctype>
using namespace std;
int m[10][10][10];
int main() {
	for (int i = 0; i < 10; i++) {
		for (int j = 0; j < 10; j++) {
			for (int k = 0; k < 10; k++) {
				m[i][j][k] = -1;
			}
		}
	}
	long long p, q, r, k;
	cin >> p >> q >> r >> k;
	p %= 10, q %= 10, r %= 10;
	m[p][q][r] = 3;
	for (long long i = 4; i <= k; i++) {
		int now = (p + q + r) % 10;
		p = q;
		q = r;
		r = now;
		if (m[p][q][r] != -1) {
			long long s = i - m[p][q][r];
			k -= m[p][q][r];
			k %= s;
			i = 0;
		}
	}
	cout << r << endl;
}