#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using vl = vector<ll>;
#define rep(i,n) for(int i=0;i<(n);i++)
#define rrep(i,n) for(int i=(n)-1;i>=0;i--)
#define rep1(i,n) for(int i=1;i<=(n);i++)
#define rrep1(i,n) for(int i=(n);i>0;i--)
#define fore(i_in,a) for (auto& i_in: a)
#define sz(x) (int)x.size()
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define cnts(x,c) count(all(x),c)
#define fio() cin.tie(nullptr);ios::sync_with_stdio(false);
#define DEBUG_CTN(v) cerr<<#v<<":";for(auto itr=v.begin();itr!=v.end();itr++) cerr<<" "<<*itr; cerr<<endl
template<class T> bool chmax(T &a, const T &b) {if (a<b) {a = b; return 1;} return 0;}
template<class T> bool chmin(T &a, const T &b) {if (a>b) {a = b; return 1;} return 0;}
template<class T> void print(const T &t) {cout<<t<<"\n";}
template<class T> void PRINT(const T &t) {rep(i,sz(t)) cout<<t[i]<<" \n"[i==sz(t)-1];}
const ll INF = 1LL << 62;
const int iINF = 1 << 30;

using ull = unsigned long long;
using mat = vector<vector<ull>>;

mat mat_mul(mat &a, mat &b) {
    mat res(sz(a), vector<ull>(sz(b[0])));
    rep(i,sz(a)) rep(j,sz(b[0])) {
        rep(l,sz(b)) res[i][j] += a[i][l] %10 * b[l][j]%10;
    }
    return res;
}

mat mat_pow(mat a, ll n) {
    mat res(sz(a), vector<ull>(sz(a)));
    rep(i,sz(a)) res[i][i] = 1;
    while(n>0) {
        if(n&1) res=mat_mul(a,res);
        a=mat_mul(a,a);
        n >>= 1;
    }
    return res;
}

ull p,q,r,k;

int main() {
    fio(); cin>>p>>q>>r>>k;
//    p%=10ULL,q%=10ULL,r%=10ULL;
    mat A={{1,1,1},{1,0,0},{0,1,0}};
    mat B={{r,0,0},{q,0,0},{p,0,0}};

    auto G = mat_pow(A,k-3);
    auto res = mat_mul(G,B);
//    fore(x,res){ DEBUG_CTN(x);}
    cout<<res[0][0]%10<<"\n";
}