#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
using ll = long long;
using ull = unsigned long long;
using ld = long double;
using pii = pair<int, int>;
using pdd = pair<double, double>;
using pll = pair<ll, ll>;
using pli = pair<ll, int>;
using pil = pair<int, ll>;
template <typename T>
using Graph = vector<vector<T>>;
const int MOD = 1e9 + 7;
const ld PI = acos(-1);

template <typename T>
struct Matrix {
    int H, W;
    vector<vector<T>> M;
    Matrix(int H_, int W_, T val = 0) : H(H_), W(W_) {
        M = vector<vector<T>>(H, vector<T>(W, val));
    }
};

template <typename T>
Matrix<T> operator*(Matrix<T> &A, Matrix<T> &B) {
    assert(A.W == B.H);

    Matrix<T> res(A.H, B.W, 0);
    for (int i = 0; i < A.H; i++) {
        for (int k = 0; k < A.W; k++) {
            for (int j = 0; j < B.W; j++) {
                (res.M[i][j] += A.M[i][k] * B.M[k][j]) %= 10;
            }
        }
    }

    return res;
}

template <typename T>
Matrix<T> operator+(Matrix<T> &A, Matrix<T> &B) {
    assert(A.H == B.H);
    assert(A.W == B.W);

    Matrix<T> res(A.H, B.W, 0);
    for (int i = 0; i < A.H; i++) {
        for (int j = 0; j < B.W; j++) {
            res.M[i][j] = (A.M[i][j] + B.M[i][j]) % 10;
        }
    }

    return res;
}

template <typename T>
Matrix<T> operator^(Matrix<T> A, ll n) {
    assert(A.H == A.W);

    Matrix<T> res(A.H, A.W, 0);
    for (int i = 0; i < A.H; ++i) {
        res.M[i][i] = 1;
    }
    while (n) {
        if (n & 1) {
            res = res * A;
        }
        A = A * A;
        n >>= 1;
    }

    return res;
}

int main() {
    cin.tie(0);
    ios::sync_with_stdio(false);

    int p, q, r;
    ll K;
    cin >> p >> q >> r >> K;
    p %= 10;
    q %= 10;
    r %= 10;

    K -= 3;
    Matrix<int> A(3, 3);
    A.M[0][0] = 1;
    A.M[0][1] = 1;
    A.M[0][2] = 1;
    A.M[1][0] = 1;
    A.M[2][1] = 1;

    A = A ^ K;

    int ans = (A.M[0][0] * r + A.M[0][1] * q + A.M[0][2] * p) % 10;
    cout << ans << endl;

    return 0;
}