#include <bits/stdc++.h>
using namespace std;
//#include <atcoder/all>
//using namespace atcoder;
using ll=long long;
using Graph=vector<vector<int>>;
#define MAX 1000000
#define MOD 1000000007
//#define INF 1000000000
#define INF 1000000000000000000

int main(){
  int p,q,r;
  ll K;
  cin>>p>>q>>r>>K;
  p%=10;
  q%=10;
  r%=10;
  vector<vector<int>> doubling(1000,vector<int>(60));
  for(int i=0;i<10;i++){
    for(int j=0;j<10;j++){
      for(int k=0;k<10;k++){
        doubling[100*i+10*j+k][0]=100*j+10*k+(i+j+k)%10;
      }
    }
  }
  for(int j=1;j<60;j++){
    for(int i=0;i<1000;i++){
      doubling[i][j]=doubling[doubling[i][j-1]][j-1];
    }
  }

  int x=100*p+10*q+r;
  K-=3;
  for(int j=0;j<60;j++){
    if(K%2==1){
      x=doubling[x][j];
    }
    K>>=1;
  }
  cout<<x%10<<endl;
}