#line 1 "/workspaces/compro/lib/template.hpp"


#line 1 "/workspaces/compro/lib/io/vector.hpp"
#include <iostream>
#include <vector>

#ifndef IO_VECTOR
#define IO_VECTOR

template <class T> std::ostream &operator<<(std::ostream &out, const std::vector<T> &v) {
  int size = v.size();
  for (int i = 0; i < size; i++) {
    std::cout << v[i];
    if (i != size - 1)
      std::cout << " ";
  }
  return out;
}

template <class T> std::istream &operator>>(std::istream &in, std::vector<T> &v) {
  for (auto &el : v) {
    std::cin >> el;
  }
  return in;
}

#endif
#line 4 "/workspaces/compro/lib/template.hpp"
#include <bits/stdc++.h>
#define REP(i, n) for (int i = 0; i < n; i++)
#define FOR(i, m, n) for (int i = m; i < n; i++)
#define ALL(v) (v).begin(), (v).end()
#define coutd(n) cout << fixed << setprecision(n)
#define ll long long int
#define vl vector<ll>
#define vi vector<int>
#define MM << " " <<

using namespace std;

template <class T> void chmin(T &a, T b) {
  if (a > b)
    a = b;
}

template <class T> void chmax(T &a, T b) {
  if (a < b)
    a = b;
}

// 重複を消す。計算量はO(NlogN)
template <class T> void unique(std::vector<T> &v) {
  std::sort(v.begin(), v.end());
  v.erase(std::unique(v.begin(), v.end()), v.end());
}


#line 2 "main.cpp"

long long solve(long long p, long long q, long long r, long long K) {
  K -= 4;

  p %= 10;
  q %= 10;
  r %= 10;
  vector<pair<int, pair<int, int>>> used;
  used.push_back({p, {q, r}});
  int tmp = (p + q + r) % 10;
  p = q;
  q = r;
  r = tmp;
  int loop_start = 0;
  while (true) {
    int len = used.size();
    bool ok = false;
    REP(i, len) {
      if (used[i].first == p && used[i].second.first == q && used[i].second.second == r) {
        loop_start = i;
        ok = true;
        break;
      }
    }
    if (ok)
      break;
    used.push_back({p, {q, r}});
    int tmp = (p + q + r) % 10;
    p = q;
    q = r;
    r = tmp;
  }

  if (K < used.size()) {
    return (used[K].first + used[K].second.first + used[K].second.second) % 10;
  }

  ll loop_size = used.size() - loop_start;
  int idx = ((K - loop_start) % loop_size) + loop_start;
  return (used[idx].first + used[idx].second.first + used[idx].second.second) % 10;
}

// generated by online-judge-template-generator v4.7.1 (https://github.com/online-judge-tools/template-generator)
int main() {
  long long p, q, r, K;
  std::cin >> p >> q >> r >> K;
  auto ans = solve(p, q, r, K);
  std::cout << ans << std::endl;
  return 0;
}