#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define ALL(v) v.begin(),v.end()
typedef long long ll;

#include <bits/stdc++.h>
using namespace std;

#define MOD 10
vector<vector<ll>> matrixmul(ll m,vector<vector<ll>> a,vector<vector<ll>> b){
  vector<vector<ll>> c(m,vector<ll>(m,0));
  rep(i,m){
    rep(j,m){
      rep(k,m) c[i][j]=(c[i][j]+a[i][k]*b[k][j]%MOD)%MOD;
    }
  }
  return c;
}

vector<vector<ll>> matrixpow(ll m,vector<vector<ll>> vec,ll n){
  vector<vector<ll>> ans(m,vector<ll>(m,0));
  rep(i,m) ans[i][i]=1;
  while(n){
    if(n&1) ans=matrixmul(m,ans,vec);
    vec=matrixmul(m,vec,vec);
    n>>=1;
  }
  return ans;
}

int main(){
  ll p,q,r,k;
  cin>>p>>q>>r>>k;
  p%=10,q%=10,r%=10;
  
  vector<vector<ll>> A(3,vector<ll> (3));
  A[0][0]=1,A[0][1]=1,A[0][2]=1,A[1][0]=1,A[2][1]=1;
  
  vector<vector<ll>> B=matrixpow(3,A,k-3);
  cout<<(r*B[0][0]+q*B[0][1]+p*B[0][2])%10<<endl;
  
  return 0;
}