#include <bits/stdc++.h>
#include <atcoder/all>
#include <string>

#define rep(i,n) for(ll i=0;i < (n);i++)
#define rep2(i, s, n) for (ll i = (s); i < (n); i++)
#define rrep(i,n) for(ll i=n-1;i>=0;i--)
#define ff first
#define ss second
#define pb push_back
#define ALL(a) (a).begin(),(a).end()

typedef long long ll;

const ll INF=1000000000000000000ll;
const ll MOD=1000000007ll;
const int MAX=5100000;

using namespace std;
using namespace atcoder;
using mint = modint1000000007;

// aよりもbが大きいならばaをbで更新する
// (更新されたならばtrueを返す)
template <typename T>
bool chmax(T &a, const T& b) {
  if (a < b) {
    a = b;  // aをbで更新
    return true;
  }
  return false;
}
// aよりもbが小さいならばaをbで更新する
// (更新されたならばtrueを返す)
template <typename T>
bool chmin(T &a, const T& b) {
  if (a > b) {
    a = b;  // aをbで更新
    return true;
  }
  return false;
}

vector<long long> fact, fact_inv, inv;
/*  init_nCk :二項係数のための前処理
    計算量:O(n)
*/
void init_nCk(int SIZE) {
    fact.resize(SIZE + 5);
    fact_inv.resize(SIZE + 5);
    inv.resize(SIZE + 5);
    fact[0] = fact[1] = 1;
    fact_inv[0] = fact_inv[1] = 1;
    inv[1] = 1;
    for (int i = 2; i < SIZE + 5; i++) {
        fact[i] = fact[i - 1] * i % MOD;
        inv[i] = MOD - inv[MOD % i] * (MOD / i) % MOD;
        fact_inv[i] = fact_inv[i - 1] * inv[i] % MOD;
    }
}
/*  nCk :MODでの二項係数を求める(前処理 int_nCk が必要)
    計算量:O(1)
*/
long long nCk(int n, int k) {
    assert(!(n < k));
    assert(!(n < 0 || k < 0));
    return fact[n] * (fact_inv[k] * fact_inv[n - k] % MOD) % MOD;
}

int main()
{
  ll p, q, r, K; cin >> p >> q >> r >> K;
  p %= 10; q %= 10; r %= 10;
  vector<int> chk(1000, 0); chk[p*100 + q*10 + r] = 2;
  int ans[1005]; ans[0] = p; ans[1] = q; ans[2] = r;

  for(ll i = 3; i <= 1004; i++){
    ans[i] = (ans[i-1] + ans[i-2] + ans[i-3]) % 10;
    if(i+1 == K){cout << ans[i] << endl; return 0;}
    ll now = ans[i-2] * 100 + ans[i-1] * 10 + ans[i];
    if(chk[now] != 0){
      ll first = chk[now]; ll cnt = i - first;
      K -= 3; K %= cnt;
      cout << ans[first + K] << endl; return 0;
    }
    chk[now] = i;
  }

  return 0;
}