#include <bits/stdc++.h>
//#include <atcoder/modint>
using namespace std;
//using namespace atcoder;
//using mint = modint1000000007;
typedef long long ll;
#define FOR(I,A,B) for(ll I = ll(A); I < ll(B); ++I)

vector< vector<ll> > E = {{1,0,0},{0,1,0},{0,0,1}};
vector< vector<ll> > A = {{1,1,1},{1,0,0},{0,1,0}};

vector<vector<ll>> calc(vector<vector<ll>> X,ll a){
	if(a == 0) return E;
	auto R = calc(X,a/2);
	vector<vector<ll>> res = {{0,0,0},{0,0,0},{0,0,0}};
	vector<vector<ll>> res1 = {{0,0,0},{0,0,0},{0,0,0}};
	FOR(i,0,3){
		FOR(j,0,3){
			FOR(k,0,3){
				( res[i][j] += R[i][k]*R[k][j] ) %= 10;
			}
		}
	}
	if(a & 1)FOR(i,0,3){
		FOR(j,0,3){
			FOR(k,0,3){
				( res1[i][j] += X[i][k]*res[k][j] ) %= 10;
			}
		}
	}
	if(a&1){
		return res1;
	}else{
		return res;
	}
}


int main(){
	ll K,p,q,r;
	cin >> p >> q >> r >> K;
	auto X = calc(A,K-3);
	ll ans = X[0][0]*r%10 + X[0][1]*q%10 + X[0][2]*p%10;
	cout << ans % 10 << endl;
}