#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace atcoder;
using mint = modint998244353;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000001

int main(){
	
	int p,q,r;
	cin>>p>>q>>r;
	
	p %= 10;
	q %= 10;
	r %= 10;
	
	long long K;
	cin>>K;
	
	K -= 3;
	
	vector nxt(60,vector<int>(1000,-1));
	
	rep(i,1000){
		int z = i%10;
		int y = (i/10)%10;
		int x= (i/100)%10;
		int w = (x+y+z)%10;
		
		nxt[0][i] = y*100 + z*10 + w;
	}
	
	rep(i,59){
		rep(j,1000){
			nxt[i+1][j] = nxt[i][nxt[i][j]];
		}
	}
	int cur = p*100 + q*10 + r;
	for(long long i=0;i<60;i++){
		if((K>>i)&1){
			cur = nxt[i][cur];
			//cout<<cur<<endl;
		}
	}
	
	cout<<cur%10<<endl;
	
	return 0;
}