#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); i++)
using namespace std;
typedef long long ll;

ll mod = 10;
vector<vector<long long>> matmul(vector<vector<long long>> A, vector<vector<long long>> B){
   int N = A.size();
   vector<vector<long long>> ans(N, vector<long long>(N, 0));
   for (int i = 0; i < N; i++){
       for (int j = 0; j < N; j++){
           for (int k = 0; k < N; k++){
               ans[i][k] += A[i][j] * B[j][k];
               ans[i][k] %= mod;
           }
       }
   }
   return ans;
}
vector<vector<long long>> matpow(vector<vector<long long>> A, long long b){
   int N = A.size();
   vector<vector<long long>> ans(N, vector<long long>(N, 0));
   for (int i = 0; i < N; i++){
       ans[i][i] = 1;
   }
   while (b > 0){
       if (b % 2 == 1){
           ans = matmul(ans, A);
       }
       A = matmul(A, A);
       b /= 2;
   }
   return ans;
}

int main(){
    cin.tie(0);
    ios::sync_with_stdio(0);

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