#include <bits/stdc++.h>

using namespace std;

const int mx = 1000 + 5;

int main() {
    int p, q, r;
    long long k;
    cin >> p >> q >> r >> k;
    k--;
    p %= 10, q %= 10, r %= 10;
    vector<int> a(mx, 0);
    a[0] = p, a[1] = q, a[2] = r;
    vector<int> used(mx, 0);
    long long ans = k;
    used[100 * r + 10 * q + 1 * p] = 2;
    for (long long i = 3; i <= k; i++) {
        long long nx = (a[i - 1] + a[i - 2] + a[i - 3]) % 10;
        long long S = nx * 100 + a[i - 1] * 10 + a[i - 2] * 1;
        a[i] = nx;
        if (used[S] != 0) {
            long long cycle = i - used[S];
            ans = (k - used[S]) % cycle + used[S];
            break;
        }
        used[S] = i;
    }
    cout << a[ans] << endl;
}