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

struct iofast_t {
    iofast_t() {
        ios::sync_with_stdio(false);
        cin.tie(nullptr);
    }
} iofast;

struct uns_t {} uns;
template <typename Element, typename Head, typename ...Args>
auto vec(Element init, Head arg, Args ...args) {
    if constexpr (sizeof...(Args) == 0) return std::vector(arg, init);
    else return std::vector(arg, vec(init, args...));
}
template <typename Element, typename Head, typename ...Args>
auto vec(uns_t, Head arg, Args ...args) {
    return vec(Element(), arg, args...);
}

template <typename T, typename Compare = less<T>>
T &chmin(T &l, T r, Compare &&f = less<T>()) { return l = min(l, r, f); }
template <typename T, typename Compare = less<T>>
T &chmax(T &l, T r, Compare &&f = less<T>()) { return l = max(l, r, f); }

int main() {
    constexpr int log2 = 60;

    int64_t p, q, r, k; cin >> p >> q >> r >> k;
    p %= 10; q %= 10; r %= 10;

    auto dub = vec<tuple<int, int, int>>(uns, log2 + 1, 10, 10, 10);
    for (int i = 0; i < 10; ++i) {
        for (int j = 0; j < 10; ++j) {
            for (int k = 0; k < 10; ++k) {
                dub[0][i][j][k] = { j, k, (i + j + k) % 10 };
            }
        }
    }

    for (int l = 1; l <= log2; ++l) {
        for (int i = 0; i < 10; ++i) {
            for (int j = 0; j < 10; ++j) {
                for (int k = 0; k < 10; ++k) {
                    auto [a, b, c]= dub[l - 1][i][j][k];
                    dub[l][i][j][k] = dub[l - 1][a][b][c];
                }
            }
        }
    }

    if (k == 1) {
        cout << p << endl;
        return 0;
    }

    if (k == 2) {
        cout << q << endl;
        return 0;
    }

    if (k == 3) {
        cout << r << endl;
        return 0;
    }

    k -= 3;
    auto iter = make_tuple(p, q, r);
    for (int i = 0; (k >> i) != 0; ++i) {
        if (!(k & (INT64_C(1) << i))) {
            continue;
        }
        auto [a, b, c] = iter;
        iter = dub[i][a][b][c];
    }

    cout << get<2>(iter) << endl;
}