#include <bits/stdc++.h>
// #include <atcoder/modint>
#define rng(a) a.begin(),a.end()
#define rrng(a) a.rbegin(),a.rend()
#define INF 2000000000000000000
#define ll long long
#define ld long double
#define pll pair<ll, ll>
using namespace std;
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  ll p, q, r, K;
  cin >> p >> q >> r >> K;
  K -= 4;
  p %= 10, q %= 10, r %= 10;
  map<vector<ll>, ll> mp;
  mp[{p, q, r}] = 0;
  ll cnt = 1;
  while (K > 0) {
    K -= 1;
    ll next = (p + q + r) % 10;
    p = q;
    q = r;
    r = next;
    if (mp.find({p, q, r}) != mp.end()) {
      break;
    }
    mp[{p, q, r}] = cnt;
    cnt += 1;
  }
  if (K == 0) {
    cout << (p + q + r) % 10 << "\n";
    return 0;
  }
  ll len = cnt - mp[{p, q, r}];
  K %= len;
  for (ll i = 0; i < K; ++i) {
    ll next = (p + q + r) % 10;
    p = q;
    q = r;
    r = next;
  }
  cout << (p + q + r) % 10 << "\n";
}