#include "bits/stdc++.h"
//#include "atcoder/all"
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
//const int mod = 1000000007;
//using mint = modint998244353;
//const int mod = 998244353;
//const int INF = 1e9;
//const long long LINF = 1e18;
//const bool debug = false;
#define rep(i, n) for (int i = 0; i < (n); ++i)
#define rep2(i,l,r)for(int i=(l);i<(r);++i)
#define rrep(i, n) for (int i = (n-1); i >= 0; --i)
#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)
#define all(x) (x).begin(),(x).end()
#define allR(x) (x).rbegin(),(x).rend()
#define endl "\n"
#define P pair<int,int>
template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }
template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }
int dp[10][10][10];
int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	int p, q, r; cin >> p >> q >> r;
	p %= 10;
	q %= 10;
	r %= 10;
	long long k; cin >> k;
	k -= 4;
	rep(i, 10)rep(j, 10)rep(k, 10)dp[i][j][k] = -1;
	dp[p][q][r] = 0;
	vector<int>memo;
	memo.push_back((p + q + r) % 10);
	while (true) {
		int np = q;
		int nq = r;
		int nr = (p + q + r) % 10;
		p = np;
		q = nq;
		r = nr;
		//cout << p << q << r << endl;
		if (-1 != dp[p][q][r])break;
		dp[p][q][r] = memo.size();
		memo.push_back((p + q + r) % 10);
	}
	int roop = memo.size() - dp[p][q][r];
	int head = memo.size() - roop;
	//cout << "roop" << roop << endl;
	//cout << "head" << head << endl;
	long long nk = k;
	if (nk >= head)nk = (nk - head) % roop + head;
	cout << memo[nk] << endl;
	return 0;
}