#include <algorithm>
#include <iostream>
#include <numeric>
#include <string>
#include <tuple>
#include <utility>
#include <vector>

#define rep(i, a, b) for (int i = int(a); i < int(b); i++)
using namespace std;
using ll = long long int;
using P = pair<ll, ll>;

// clang-format off
#ifdef _DEBUG_
#define dump(...) do{ cerr << __LINE__ << ":\t" << #__VA_ARGS__ << " = "; debug_print(__VA_ARGS__); } while(false)
template<typename T, typename... Ts> void debug_print(const T &t, const Ts &...ts) { cerr << t; ((cerr << ", " << ts), ...); cerr << endl; }
#else
#define dump(...) do{ } while(false)
#endif
template<typename T> vector<T> make_v(size_t a, T b) { return vector<T>(a, b); }
template<typename... Ts> auto make_v(size_t a, Ts... ts) { return vector<decltype(make_v(ts...))>(a, make_v(ts...)); }
template<typename T> bool chmin(T &a, const T& b) { if (a > b) {a = b; return true; } return false; }
template<typename T> bool chmax(T &a, const T& b) { if (a < b) {a = b; return true; } return false; }
template<typename T, typename... Ts> void print(const T& t, const Ts&... ts) { cout << t; ((cout << ' ' << ts), ...); cout << '\n'; }
template<typename... Ts> void input(Ts&... ts) { (cin >> ... >> ts); }
template<typename T> istream &operator,(istream &in, T &t) { return in >> t; }
// clang-format on

using matrix = vector<vector<int>>;

matrix multiple(const matrix &m1, const matrix &m2) {
    matrix res = make_v(3, 3, 0);
    rep(i, 0, 3) {
        rep(j, 0, 3) {
            rep(k, 0, 3) {
                res[i][j] += m1[i][k] * m2[k][j];
            }
            res[i][j] %= 10;
        }
    }

    return res;
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int p, q, r;
    ll k;
    cin, p, q, r, k;
    p %= 10;
    q %= 10;
    r %= 10;

    matrix mat = make_v(3, 3, 0);
    mat[0][0] = mat[0][1] = mat[0][2] = mat[1][0] = mat[2][1] = 1;
    matrix init = make_v(3, 3, 0);
    init[0][0] = init[1][1] = init[2][2] = 1;
    matrix ans = init;
    k -= 3;
    while (k) {
        if (k & 1) {
            ans = multiple(ans, mat);
        }
        mat = multiple(mat, mat);
        k >>= 1;
    }

    print((ans[0][0] * r + ans[0][1] * q + ans[0][2] * p) % 10);

    return 0;
}