#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;

// デバッグ表示
#define dump(x) cout << #x << ":" << (x) << endl;

// 型定義
typedef long long ll;
typedef pair<ll, ll> P;

// forループ
#define REP(i,n) for(ll i=0; i<(ll)(n); ++i)

// 定数宣言
const int INF = 1e9;
const int MOD = 1e9+7;
const ll LINF = 1e18;

// modint
using mint = modint1000000007;
// using mint = modint998244353;

// グラフ表現
using Graph = vector<vector<int>>;

// グラフの辺表現
using Edge = map<pair<int,int>,int>;

// n次元配列の初期化。第２引数の型のサイズごとに初期化していく。
template<typename A, size_t N, typename T>
void Fill(A (&array)[N], const T &val){
    std::fill( (T*)array, (T*)(array+N), val );
}

// コンビネーションを計算する関数
ll pow(ll N, ll k) {
    ll res = 1;
    for (ll i = 0; i < k; ++i) res *= N;
    return res;
}

// 最大公約数
ll gcd(ll a,ll b){
   if (a%b == 0) return(b);
   else return(gcd(b, a%b));
}

// 最小公倍数
ll lcm(ll a, ll b){
    return a/gcd(a, b) * b;
}

int main()
{
    cout << fixed << setprecision(15);
    ll po, qo, ro, K;
    cin >> po >> qo >> ro >> K;

    if(K <= 100000){
        ll p = po % 10;
        ll q = qo % 10;
        ll r = ro % 10;
        
        REP(i, K-3){
            ll temp = (p+q+r) % 10;
            p = q;
            q = r;
            r = temp;
        }
        cout << r << endl;
        return 0;
    }
    
    map<ll, ll> M;
    ll p = po % 10;
    ll q = qo % 10;
    ll r = ro % 10;
    
    ll t = 100*p+10*q+r;
    M[t] = 1;
    bool check = false;
    for(ll i=1; i<=K-3; i++){
        ll temp = (p+q+r) % 10;
        p = q;
        q = r;
        r = temp;

        t = 100*p+10*q+r;
        if(check == false && M[t] != 0){
            ll u = (i+1) - M[t];

            ll m = (K-3) - i;
            ll n = m / u;
            i += u * n;
            check = true;
            // dump(i);
        }
        M[t] = i+1;
    }

    cout << r << endl;
        
    return 0;
}