#include<bits/stdc++.h>
#define int long long
using namespace std;
using ll=long long;
using Mat=std::vector<std::vector<ll>>;
constexpr ll mod=10;
Mat operator*(Mat a,Mat b){
    Mat res(a.size(),std::vector<ll>(b[0].size()));
    for(int i=0;i<(int)a.size();i++){
        for(int j=0;j<(int)b[0].size();j++){
            for(int k=0;k<(int)b.size();k++)(res[i][j]+=a[i][k]*b[k][j])%=mod;
        }
    }
    return res;
}
Mat mat_e(unsigned int sz){
    Mat res(sz,std::vector<ll>(sz));
    for(int i=0;i<(int)sz;i++)res[i][i]=1;
    return res;
}
Mat mat_pow(Mat a,ll b){
    if(!b)return mat_e(a.size());
    if(b&1)return mat_pow(a,b-1)*a;
    return mat_pow(a*a,b/2);
}
signed main(){
    int p,q,r,K; cin>>p>>q>>r>>K;
    vector<vector<int>> A{{1,1,1},{1,0,0},{0,1,0}};
    vector<vector<int>> B{{r%10},{q%10},{p%10}};
    cout<<(mat_pow(A,K-1)*B)[2][0]<<endl;
}