#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using pll = pair<ll, ll>;
using tlll = tuple<ll, ll, ll>;
constexpr ll MOD = 1e9 + 7;
//constexpr ll MOD = 998244353;
//constexpr ll MOD = ;
ll mod(ll A, ll M) {return (A % M + M) % M;}
constexpr ll INF = 1LL << 60;
template<class T> bool chmin(T& a, T b) {if (a > b) {a = b; return true;} return false;}
template<class T> bool chmax(T& a, T b) {if (a < b) {a = b; return true;} return false;}
ll divceil(ll A, ll B) {return (A + (B - 1)) / B;}
#define FINALANS(A) do {cout << (A) << '\n'; exit(0);} while (false)

int main()
{
  ll p, q, r, K;
  cin >> p >> q >> r >> K;
  p %= 10, q %= 10, r %= 10;

  tlll pqr = make_tuple(p, q, r);
  map<tlll, ll> mp;
  mp[pqr] = 0;
  vector<tlll> his;
  his.push_back(pqr);
  ll L, R;
  for (ll k = 1; k < 1333; k++)
  {
    ll s = (p + q + r) % 10;
    p = q, q = r, r = s;

    tlll pqr = make_tuple(p, q, r);
    if (mp.count(pqr) == 0)
      mp[pqr] = k;
    else
    {
      L = mp[pqr], R = k;
      break;
    }
    his.push_back(pqr);
  }

  ll x = (K - 3 - L) % (R - L);
  ll ans = get<2>(his.at(L + x));
  cout << ans << endl;

  /*
  ll i = 0;
  for (auto pqr : his)
  {
    ll p = get<0>(pqr), q = get<1>(pqr), r = get<2>(pqr);
    cerr << i << "  " << p << " " << q << " " << r << endl;
    i++;
  }
  cerr << L << " " << R << endl;
  //*/
}