#include <bits/stdc++.h>
#define rep(i, l, r) for (int i = (l); i < (r); i++)
using namespace std;

typedef long long ll;

int main() {
    int p, q, r;
    ll K;
    cin >> p >> q >> r >> K;
    p %= 10;
    q %= 10;
    r %= 10;
    int a[10][10][10];
    rep(i, 0, 10) rep(j, 0, 10) rep(k, 0, 10) a[i][j][k] = -1;
    for (ll i = 1; i < K; i++) {
        if (a[p][q][r] == -1) {
            a[p][q][r] = i;
        } else {
            K = (K - i) % (i - a[p][q][r]) + i;
        }
        p = (p + q + r) % 10;
        swap(p, q);
        swap(q, r);
        //cout << p << q << r << endl;
    }
    cout << p << endl;
}