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

#ifdef LOCAL
#include "debug.hpp"
#define debug(...) cerr << "[" << #__VA_ARGS__ << "]:", debug_out(__VA_ARGS__)
#else
#define debug(...)
#endif

ll f (ll a, ll b, ll c) {
  return (a + b + c) % 10;
}

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

  ll p; cin >> p;
  ll q; cin >> q;
  ll r; cin >> r;
  ll K; cin >> K;
  vector<vector<vector<ll>>> memo(10, vector<vector<ll>>(10, vector<ll>(10, -1)));
  vector<ll> time_stamp(1000, -1);
  ll a1 = p % 10, a2 = q % 10, a3 = r % 10;
  ll pos = a1 * 100 + a2 * 10 + a3, cnt = 0;

  while (time_stamp[pos] == -1) {
    time_stamp[pos] = cnt;
    ll a4 = f(a1, a2, a3);
    a1 = a2;
    a2 = a3;
    a3 = a4;
    pos = a1 * 100 + a2 * 10 + a3;
    cnt++;
    debug(cnt, a4);
  }
  debug(pos);

  ll loop = cnt - time_stamp[pos];
  if (K >= loop) {
    K = time_stamp[pos] + ((K - time_stamp[pos]) % loop);
  }
  K += loop - 3;
  debug(K);

  a1 = p % 10, a2 = q % 10, a3 = r % 10;
  cnt = 1;
  while (true) {
    if (cnt == K) {
      break;
    }
    ll a4 = f(a1, a2, a3);
    a1 = a2;
    a2 = a3;
    a3 = a4;
    cnt++;
  }

  ll ans = f(a1, a2, a3);
  cout << ans << '\n';
  return 0;
}