#ifdef __LOCAL
#define _GLIBCXX_DEBUG
#endif
#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<int,int>;
using PIL = pair<int,ll>;
using PLI = pair<ll,int>;
using PLL = pair<ll,ll>;

template<class T> bool chmin(T &a, T b) {if(a>b){a=b;return 1;}return 0;}
template<class T> bool chmax(T &a, T b) {if(a<b){a=b;return 1;}return 0;}
template<class T> void show_vec(T v) {for (int i=0;i<v.size();i++) cout<<v[i]<<endl;}
template<class T> void show_pair(T p) {cout<<p.first<<" "<<p.second<<endl;}
template<class T> bool judge_digit(T bit,T i) {return (((bit&(1LL<<i))!=0)?1:0);}
#define REP(i,n) for(int i=0;i<int(n);i++)
#define ROUNDUP(a,b) (((a)+(b)-1)/(b))
#define YESNO(T) cout<<(T?"YES":"NO")<<endl
#define yesno(T) cout<<(T?"yes":"no")<<endl
#define YesNo(T) cout<<(T?"Yes":"No")<<endl

const int INFint = 1 << 29;
const ll INF = 1LL << 60;
const ll MOD = 1000000007LL;
const double pi = 3.14159265358979;
const vector<int> h_idx4 = {-1, 0,0,1};
const vector<int> w_idx4 = { 0,-1,1,0};
const vector<int> h_idx8 = {-1,-1,-1, 0,0, 1,1,1};
const vector<int> w_idx8 = {-1, 0, 1,-1,1,-1,0,1};

// (an * am)行列A と (bn * bm)行列B の積を求める
// am == bn のとき, (an * bm)行列を返す
vector<vector<ll>> Matrix_product(vector<vector<ll>> &A,vector<vector<ll>> &B){
    int an = A.size(),bn = B.size();
    int am = A[0].size(),bm = B[0].size();
    assert(am == bn);

    vector<vector<ll>> res(an, vector<ll>(bm,0));
    for (int i = 0; i < an; i++){
        for (int j = 0; j < bm; j++){
            for (int k = 0; k < am; k++){
                res[i][j] += A[i][k] * B[k][j];
                res[i][j] %= 10;
            }
        }
    }

    return res;
}

// 行列Mに対し,M^nを返す (n >= 0)
vector<vector<ll>> Matrix_pow(vector<vector<ll>> &M,ll n){
    int x = M.size();
    int y = M[0].size();
    assert(n >= 0 && x == y);

    vector<vector<ll>> res(x, vector<ll>(x,0)); // 単位行列
    for (int i = 0; i < x; i++){
        res[i][i] = 1;
    }

    vector<vector<ll>> a = M;

    while (n > 0){
        if (n & 1) res = Matrix_product(res,a);
        a = Matrix_product(a,a);
        n >>= 1;
    }
    return res;
}

void show_Matrix(vector<vector<ll>> &M){
    for (int i = 0; i < M.size(); i++){
        for (int j = 0; j < M[i].size(); j++){
            cout << M[i][j] << " ";
        }
        cout << endl;
    }

    return;
}

int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(15);

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

    vector<vector<ll>> M(3, vector<ll>(3,0));
    M[0][2] = 1;
    M[1][0] = 1;
    M[1][2] = 1;
    M[2][1] = 1;
    M[2][2] = 1;

    M = Matrix_pow(M,(k - 3));
    vector<vector<ll>> x(1, vector<ll>(3));
    x[0][0] = p;
    x[0][1] = q;
    x[0][2] = r;

    vector<vector<ll>> L = Matrix_product(x,M);
    cout << L[0][2] << endl;



}