#include <bits/stdc++.h>
using namespace std;
const int 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>> matexp(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(){
  int p, q, r;
  long long K;
  cin >> p >> q >> r >> K;
  K--;
  vector<int> A(1200);
  A[0] = p % 10;
  A[1] = q % 10;
  A[2] = r % 10;
  for (int i = 3; i < 1200; i++){
    A[i] = (A[i - 1] + A[i - 2] + A[i - 3]) % 10;
  }
  if (K < 1200){
    cout << A[K] << endl;
  } else {
    int c;
    for (int i = 1; i < 1100; i++){
      int x = A[1197] * 100 + A[1198] * 10 + A[1199];
      int y = A[1197 - i] * 100 + A[1198 - i] * 10 + A[1199 - i];
      if (x == y){
        c = i;
        break;
      }
    }
    int r = K % c;
    while (true){
      int r2 = r + c;
      if (r2 >= 1200){
        break;
      }
      r = r2;
    }
    cout << A[r] << endl;
  }
}