#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;
    vector<int> ans(10000);
    rep(i, 1, 4) {
        cin >> ans[i];
        ans[i] %= 10;
    }
    cin >> K;
    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++) {
        int x = a[ans[i]][ans[i + 1]][ans[i + 2]];
        if (x == -1) {
            a[ans[i]][ans[i + 1]][ans[i + 2]] = i;
        } else {
            K = (K - i) % (i - x) + i;
        }
        ans[i + 3] = (ans[i] + ans[i + 1] + ans[i + 2]) % 10;
    }
    cout << ans[K] << endl;
}