#include<bits/stdc++.h>
#include <atcoder/all>
#define ll long long int
#define vec vector<ll>
#define mat vector<vector<ll>>
#define pll pair<ll,ll>
#define count __builtin_popcountll

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

const ll mod=1000000007;//998244353;
const ll inf=1000000000000000000;
ll dx4[4]={1,0,-1,0};
ll dy4[4]={0,-1,0,1};
ll dx8[8]={1,0,-1,1,-1,1,0,-1};
ll dy8[8]={1,1,1,0,0,-1,-1,-1};

ll f(ll a,ll b,ll c){
  return 100*a+10*b+c;
}

void g(ll &a,ll &b,ll &c){
  ll d=(a+b+c)%10;
  a=b;
  b=c;
  c=d;
  return;
}

int main(){
  cout << fixed << setprecision(15);

  ll p,q,r,k;
  cin >> p >> q >> r >> k; 
  p%=10;
  q%=10;
  r%=10;
  vec a(3);
  a[0]=p;
  a[1]=q;
  a[2]=r;

  vec s(1000);
  ll e=0;
  s[f(a[0],a[1],a[2])]++;
  while(1){
    g(a[0],a[1],a[2]);
    e++;
    if(s[f(a[0],a[1],a[2])]>0)break;
    s[f(a[0],a[1],a[2])]++;
    // cout << e << " " << a[2] << endl;
  }
  ll c=f(a[0],a[1],a[2]);

  ll d=0;
  vec b(3);
  b[0]=p;
  b[1]=q;
  b[2]=r;
  while(f(b[0],b[1],b[2])!=c){
    g(b[0],b[1],b[2]);
    d++;
  }

  k-=3;

  // cout << d << " " << e << endl;

  if(k<=d){
    for(ll i=0;i<k;i++){
      g(p,q,r);
    }
    cout << r << endl;
  }
  else{
    k=k-d;
    k%=(e-d);
    for(ll i=0;i<d;i++){
      g(p,q,r);
    }
    for(ll i=0;i<k;i++){
      g(p,q,r);
    }
    cout << r << endl;
  }


  

  return 0;
}