#if !__INCLUDE_LEVEL__

#include __FILE__
//行列の積
#define mat vector<vector<ll>>
const ll MOD = 10;
mat mat_mul(mat &b, mat &a) {
    mat res(a.size(), vector<ll>(b[0].size()));
    for (int i = 0; i < a.size(); i++) {
        for (int j = 0; j < b[0].size(); j++) {
            for (int k = 0; k < b.size(); k++) {
                (res[i][j] += a[i][k] * b[k][j]) %= MOD;
            }
        }
    }
    return res;
}
/// 行列累乗
mat mat_pow(mat a, long long n) {
    mat res(a.size(), vector<ll>(a.size()));
    // 単位行列で初期化
    for (int i = 0; i < a.size(); i++)res[i][i] = 1;
    // 繰り返し二乗法
    while (n > 0) {
        if (n & 1) res = mat_mul(res,a);
        a = mat_mul(a, a);
        n >>= 1;
        }
    return res;
}
//MODのデフォは1000000007
//遷移表AのK回遷移後
//mat L=mat_pow(A,K);
//mat R(1,vl(N,1));
//mat Ans(1,vl(N,0));
//Ans = mat_mul(L,R);
//書きがちの遷移行列、縦と横がプログラム上だと逆なので注意
int main()
{
    ll P,Q,R,K;cin >> P >> Q >> R >> K;
    mat A(3,vl(3,0));
    A[0][2]=1;
    A[1][2]=1;
    A[2][2]=1;
    A[2][1]=1;
    A[1][0]=1;
    mat r = mat_pow(A,K-3);
    //rep(i,3)cout << r[i] << endl;
    mat L(1,vl(3,1));
    L[0][0]=P%10;
    L[0][1]=Q%10;
    L[0][2]=R%10;
    mat Ans(1,vl(3,0));
    Ans = mat_mul(r,L);
    cout << Ans[0][2] << "\n";
}

#else
//tie(a, b, c) = t
//repをllにしているので時間ギリギリならintに変換
#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
#define rep(i, n) for(long long int i = 0; i < n; i++)
#define rrep(i, n) for(long long int i = n-1; i >= 0; i--)
#define range(i, m, n) for(long long int i = m; i < n; i++)
#define fore(i,a) for(auto &i:a)
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define Sum(v) accumulate(all(v),0LL)
#define minv(v) *min_element(all(v))
#define maxv(v) *max_element(all(v))
typedef long long ll;
typedef vector<ll> vl;
typedef vector<vector<ll>> vvl;
const ll INF = 1e16;
const ll MOD1 = 1000000007;
const ll MOD2 = 998244353;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
ll SN(char s){return ll(s-'0');}
ll SN(string s){return stoll(s);}
int alpN(char s){return int(s-'a');}
int AlpN(char s){return int(s-'A');}
int Nalp(int n){return char(n+97);}
int NAlp(int n){return char(n+65);}
using Graph = vector<vector<ll>>;
using GraphCost = vector<vector<pair<ll,ll>>>;
using mint = modint;
using mint1 = modint1000000007;
using mint2 = modint998244353;
using pll = pair<long long, long long>;
template <class T>ostream &operator<<(ostream &o,const vector<T>&v){for(int i=0;i<(int)v.size();i++)o<<(i>0?" ":"")<<v[i];return o;}//vector空白区切り出力
ostream& operator<<(ostream& os, const mint1& N) {return os << N.val();}//mint出力。デフォはmint1
ostream& operator<<(ostream& os, const mint2& N) {return os << N.val();}
template<class T> bool contain(const std::string& s, const T& v) {
    return s.find(v) != std::string::npos;
}
ll max(int x,ll y){return max((ll)x,y);}
ll max(ll x,int y){return max(x,(ll)y);}
ll min(int x,ll y){return min((ll)x,y);}
ll min(ll x,int y){return min(x,(ll)y);}
template <typename T>
struct edge {
    int src, to;
    T cost;
    edge(int to, T cost) : src(-1), to(to), cost(cost) {}
    edge(int src, int to, T cost) : src(src), to(to), cost(cost) {}
    edge& operator=(const int& x) {
        to = x;
        return *this;
    }
    operator int() const { return to; }
};

template <typename T>
using Edges = vector<edge<T> >;
template <typename T>
using WeightedGraph = vector<Edges<T> >;
using UnWeightedGraph = vector<vector<int> >;
template <typename T>
using Matrix = vector<vector<T> >;

//unorderd_mapの拡張…https://qiita.com/hamamu/items/4d081751b69aa3bb3557
template<class T> size_t HashCombine(const size_t seed,const T &v){
    return seed^(std::hash<T>()(v)+0x9e3779b9+(seed<<6)+(seed>>2));
}
/* pair用 */
template<class T,class S> struct std::hash<std::pair<T,S>>{
    size_t operator()(const std::pair<T,S> &keyval) const noexcept {
        return HashCombine(std::hash<T>()(keyval.first), keyval.second);
    }
};
/* vector用 */
template<class T> struct std::hash<std::vector<T>>{
    size_t operator()(const std::vector<T> &keyval) const noexcept {
        size_t s=0;
        for (auto&& v: keyval) s=HashCombine(s,v);
        return s;
    }
};
/* tuple用 */
template<int N> struct HashTupleCore{
    template<class Tuple> size_t operator()(const Tuple &keyval) const noexcept{
        size_t s=HashTupleCore<N-1>()(keyval);
        return HashCombine(s,std::get<N-1>(keyval));
    }
};
template <> struct HashTupleCore<0>{
    template<class Tuple> size_t operator()(const Tuple &keyval) const noexcept{ return 0; }
};
template<class... Args> struct std::hash<std::tuple<Args...>>{
    size_t operator()(const tuple<Args...> &keyval) const noexcept {
        return HashTupleCore<tuple_size<tuple<Args...>>::value>()(keyval);
    }
};
ll ceil(ll a, ll b){
  return (a + b - 1) / b;
}
#endif