#pragma GCC optimize("Ofast")
#include <iostream>
#include <vector>
#include <algorithm>
#include <map>
#include <queue>
#include <cstdio>
#include <ctime>
#include <assert.h>
#include <chrono>
#include <random>
#include <numeric>
#include <set>
#include <deque>
#include <stack>
#include <sstream>
#include <utility>
#include <cstring>
#include <unordered_map>
#include <unordered_set>
#include <tuple>
#include <array>
#include <bitset>
using namespace std;
typedef long long int ll;
typedef unsigned long long ull;

mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
ll myRand(ll B) {
    return (ull)rng() % B;
}
inline double time() {
    return static_cast<long double>(chrono::duration_cast<chrono::nanoseconds>(chrono::steady_clock::now().time_since_epoch()).count()) * 1e-9;
}

constexpr ll mod=10;

template<class T>

struct Mat{
    vector<vector<T>> A;
    Mat(){}
    Mat(size_t n,size_t m):A(n,vector<T>(m,0)){}
    Mat(size_t n):A(n,vector<T>(n,0)){};
    size_t height() const{
        return A.size();
    }
    size_t width() const{
        return A[0].size();
    }
    inline const vector<T> &operator[](int k) const{
        return A.at(k);
    }
    inline vector<T> &operator[](int k){
        return A.at(k);
    }
    static Mat I(size_t n){
        Mat mat(n);
        for(int i=0;i<n;i++){
            mat[i][i]=1;
        }
        return mat;
    }
    Mat &operator+=(const Mat &B){
        size_t n=height(),m=width();
        for(int i=0;i<n;i++){
            for(int j=0;j<m;j++){
                (*this)[i][j]=((*this)[i][j]+B[i][j])%mod;
            }
        }
        return (*this);
    }
    Mat &operator-=(const Mat &B){
        size_t n=height(),m=width();
        for(int i=0;i<n;i++){
            for(int j=0;j<m;j++){
                (*this)[i][j]=((*this)[i][j]-B[i][j])%mod;
                if((*this)[i][j]<0)(*this)[i][j]+=mod;
            }
        }
        return (*this);
    }
    Mat &operator*=(const Mat &B){
        int n=height(),m=B.width(),p=width();
        assert(p==B.height());
        vector<vector<T>> C(n,vector<T>(m,0));
        for(int i=0;i<n;i++){
            for(int j=0;j<m;j++){
                for(int k=0;k<p;k++){
                    C[i][j]=(C[i][j]+(*this)[i][k]*B[k][j])%mod;
                }
            }
        }
        A.swap(C);
        return (*this);
    }
    Mat &operator^=(ll k){
        Mat B=Mat::I(height());
        while(k){
            if(k%2)B*=(*this);
            (*this)*=(*this);
            k>>=1LL;
        }
        A.swap(B.A);
        return (*this);
    }
    Mat operator+(const Mat &B) const{
        return (Mat(*this)+=B);
    }
    Mat operator-(const Mat &B) const{
        return (Mat(*this)-=B);
    }
    Mat operator*(const Mat &B) const{
        return (Mat(*this)*=B);
    }
    Mat operator^(const Mat &B) const{
        return (Mat(*this)^=B);
    }
};

int main(){
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    ll p,q,r,k; cin >> p >> q >> r >> k;
    p %= mod;
    q %= mod;
    r %= mod;
    Mat<ll> A(3,3);
    A[0][0] = 1; A[0][1] = 1; A[0][2] = 1;
    A[1][0] = 1;
    A[2][1] = 1;
    Mat<ll> B(3,1);
    B[0][0] = r, B[1][0] = q, B[2][0] = p;
    A ^= k-3;
    B = A*B;
    cout << B[0][0] << endl;
}