#include<bits/stdc++.h>
// #include<atcoder/all>
// #include<boost/multiprecision/cpp_int.hpp>

using namespace std;
// using namespace atcoder;
// using bint = boost::multiprecision::cpp_int;
using ll = long long;
using ull = unsigned long long;
using P = pair<int,int>;
#define rep(i,n) for(ll i = 0;i < (ll)n;i++)
#define ALL(x) (x).begin(),(x).end()
#define MOD 1000000007

void ch(ll &a,ll &b,ll &c){
  int k = (a+b+c)%10;
  a = b;b = c;c = k;
}

int main(){
  
  ll p,q,r,K;
  cin >> p >> q >> r >> K;
  p %= 10;q %= 10;r %= 10;
  vector<vector<vector<int>>> memo(10,vector<vector<int>>(10,vector<int>(10,-1)));
  memo[p][q][r] = 1;
  int l = 0,loop = 1;
  for(int i = 2;i <= 100000;i++){
    ch(p,q,r);
    if(i == K){
      cout << p << "\n";
      return 0;
    }
    if(memo[p][q][r] != -1){
      l = memo[p][q][r] - 1;
      loop -= l;
      break;
    }
    loop++;
    memo[p][q][r] = loop;
  }
  K -= l+1;
  K %= loop;
  while(K--)ch(p,q,r);
  cout << p << "\n";


  return 0;
}