#include <bits/stdc++.h>
//#include<boost/multiprecision/cpp_int.hpp>
//#include<boost/multiprecision/cpp_dec_float.hpp>
//#include <atcoder/all>
using namespace std;
#define rep(i, a) for (int i = (int)0; i < (int)a; ++i)
#define rrep(i, a) for (int i = (int)a; i > -1; --i)
#define REP(i, a, b) for (int i = (int)a; i < (int)b; ++i)
#define RREP(i, a, b) for (int i = (int)a; i > b; --i)
#define repl(i, a) for (ll i = (ll)0; i < (ll)a; ++i)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define popcount __builtin_popcount
#define popcountll __builtin_popcountll
#define fi first
#define se second
using ll = long long;
constexpr ll mod = 1e9 + 7;
constexpr ll mod_998244353 = 998244353;
constexpr ll INF = 1LL << 60;

// #pragma GCC target("avx2")
// #pragma GCC optimize("O3")
// #pragma GCC optimize("unroll-loops")

// using lll=boost::multiprecision::cpp_int;
// using
// Double=boost::multiprecision::number<boost::multiprecision::cpp_dec_float<128>>;//仮数部が1024桁
template <class T>
inline bool chmin(T &a, T b)
{
  if (a > b)
  {
    a = b;
    return true;
  }
  return false;
}
template <class T>
inline bool chmax(T &a, T b)
{
  if (a < b)
  {
    a = b;
    return true;
  }
  return false;
}

ll mypow(ll x, ll n, const ll &p = -1)
{ // x^nをmodで割った余り

  if (p != -1)
  {
    x = (x % p + p) % p;
  }
  ll ret = 1;
  while (n > 0)
  {
    if (n & 1)
    {
      if (p != -1)
        ret = (ret * x) % p;
      else
        ret *= x;
    }
    if (p != -1)
      x = (x * x) % p;
    else
      x *= x;
    n >>= 1;
  }
  return ret;
}

struct myrand{
  random_device seed;
  mt19937 mt;
  myrand():mt(seed()){}
  int operator()(int a,int b){//[a,b)
    uniform_int_distribution<int>dist(a,b-1);
    return dist(mt);
  }
};

//using namespace atcoder;

//------------------------
//------------------------
//------------------------
//------------------------
//------------------------

void solve()
{
  ll p,q,r,k;
  cin>>p>>q>>r>>k;

  p%=10,q%=10,r%=10;
  vector<vector<int>>dp(61,vector<int>(1000,-1));
  rep(i,10){
    rep(j,10){
      rep(x,10){
        dp[0][i*100+j*10+x]=j*100+x*10+(i+j+x)%10;
      }
    }
  }
  rep(i,60){
    rep(j,1000){
      if(dp[i][j]>-1)dp[i+1][j]=dp[i][dp[i][j]];
    }
  }
  int cur=p*100+q*10+r;
  k-=3;
  rep(i,61){
    if(k>>i&1){
      cur=dp[i][cur];
    }
  }
  cur%=10;
  cout<<cur<<"\n";
}

int main()
{
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  cout << fixed << setprecision(15);
  solve();
  return 0;
}