#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <cmath>
#include <vector>
#include <set>
#include <map>
#include <unordered_set>
#include <unordered_map>
#include <queue>
#include <ctime>
#include <cassert>
#include <complex>
#include <string>
#include <cstring>
#include <chrono>
#include <random>
#include <bitset>
#include <fstream>
#include <array>
using namespace std;
#define int long long
#define ii pair <int, int>
#define app push_back
#define all(a) a.begin(), a.end()
#define bp __builtin_popcountll
#define ll long long
#define mp make_pair
#define x first
#define y second
#define Time (double)clock()/CLOCKS_PER_SEC
#define debug(x) std::cerr << #x << ": " << x << '\n';

#define FORI(i,a,b) for (int i = (a); i < (b); ++i)
#define FOR(i,a) FORI(i,0,a)
#define ROFI(i,a,b) for (int i = (b)-1; i >= (a); --i)
#define ROF(i,a) ROFI(i,0,a)
#define rep(a) FOR(_,a)
#define each(a,x) for (auto& a: x)
#define FORN(i, n) FORI(i, 1, n + 1)

using vi = vector<int>;
template <typename T>
std::istream& operator >>(std::istream& input, std::pair <T, T> & data)
{
    input >> data.x >> data.y;
    return input;
}
template <typename T>
std::istream& operator >>(std::istream& input, std::vector<T>& data)
{
    for (T& x : data)
        input >> x;
    return input;
}
template <typename T>
std::ostream& operator <<(std::ostream& output, const pair <T, T> & data)
{
    output << "(" << data.x << "," << data.y << ")";
    return output;
}
template <typename T>
std::ostream& operator <<(std::ostream& output, const std::vector<T>& data)
{
    for (const T& x : data)
        output << x << " ";
    return output;
}
std::ostream& operator <<(std::ostream& output, const __int128 &x)
{
    __int128 n = x;
    if (n == 0) {
        output << "0";
        return output;
    }
    if (n < 0) {
        n = -n;
        output << "-";
    }
    string s;
    while (n) {
        s += '0' + (n%10);
        n /= 10;
    }
    reverse(all(s));
    cout << s;
    return output;
}
ll div_up(ll a, ll b) { return a/b+((a^b)>0&&a%b); } // divide a by b rounded up
ll div_down(ll a, ll b) { return a/b-((a^b)<0&&a%b); } // divide a by b rounded down 
ll math_mod(ll a, ll b) { return a - b * div_down(a, b); }
#define tcT template<class T
#define tcTU tcT, class U
tcT> using V = vector<T>; 
tcT> bool ckmin(T& a, const T& b) {
    return b < a ? a = b, 1 : 0; 
} // set a = min(a,b)
tcT> bool ckmax(T& a, const T& b) {
    return a < b ? a = b, 1 : 0; 
}
ll gcd(ll a, ll b) {
    while (b) {
        tie(a, b) = mp(b, a % b);
    }
    return a;
}
int Bit(int mask, int bit) { return (mask >> bit) & 1; }

const int N = 3;

int mul(int a, int b) {
    return a*b%10;
}
void add(int &a, int b) {
    a += b;
    a %= 10;
}

struct Matrix {
int a[N][N];
Matrix () {
    memset(a, 0, sizeof a);
}   
Matrix (bool t) {
    memset(a, 0, sizeof a);
    for (int i = 0; i < N; ++i)
        a[i][i] = t;
}   
int * operator [] (int i) {
    return a[i];
}   
Matrix operator + (Matrix b) {
    Matrix ans;
    for (int i = 0; i < N; ++i)
        for (int j = 0; j < N; ++j) {
            add(ans[i][j], a[i][j]);
            add(ans[i][j], b[i][j]);
        }
    return ans;
}   
Matrix operator * (Matrix b) {
    Matrix ans;
    for (int i = 0; i < N; ++i)
        for (int j = 0; j < N; ++j)
            for (int k = 0; k < N; ++k)
                add(ans[i][j], mul(a[i][k], b[k][j]));
    return ans;
}   
void operator *= (Matrix b) {
    *this = *this * b;
}   
void print() {
    for (int i = 0; i < N; ++i) {
        for (int j = 0; j < N; ++j) 
            cout << a[i][j] << ' ';
        cout << '\n';
    }   
    cout << '\n';
}
Matrix operator ^ (int p) { 
    Matrix cur = *this;
    Matrix ans(1);
    for (int i = 0; (1ll << i) <= p; ++i) {
        if ((p >> i) & 1) 
            ans *= cur;
        cur *= cur;
    }       
    return ans;
}   
void operator ^= (int p) {
    *this = *this ^ p;
}   
};


signed main() {
    #ifdef LOCAL
    #else
    #define endl '\n'
    ios_base::sync_with_stdio(0); cin.tie(0);
    #endif
    int p, q, r, k;
    cin >> p >> q >> r >> k;

    Matrix M;
    M[1][0] = 1;
    M[2][1] = 1;
    M[0][2] = M[1][2] = M[2][2] = 1;
    M ^= k - 3;

    cout << (p * M[0][2] + q * M[1][2] + r * M[2][2])%10 << endl;
}