#include<bits/stdc++.h>
using namespace std;
using ll = long long;
using ld = long double;
using pint = pair<int, int>;
using pll = pair<ll, ll>;

vector<vector<vector<int>>> cyc(10, vector<vector<int>>(10, vector<int>(10)));

void init_cyc(){
    for(int i = 0; i < 10; i++){
        for(int j = 0; j < 10; j++){
            for(int k = 0; k < 10; k++){
                cyc[i][j][k] = (i + j + k) % 10;
            }
        }
    }
}

int main(){
    ll p, q, r, K; cin >> p >> q >> r >> K;
    p %= 10LL; q %= 10LL; r %= 10LL; K -= 4LL;
    init_cyc();
    vector<vector<vector<int>>> time_stamp(10, vector<vector<int>>(10, vector<int>(10, -1)));
    time_stamp[p][q][r] = 0;
    int temp;
    temp = p; p = q; q = r; r = cyc[temp][p][q];
    while(time_stamp[p][q][r] == -1){
        time_stamp[p][q][r] = time_stamp[temp][p][q] + 1;
        temp = p; p = q; q = r; r = cyc[temp][p][q];
    }
    ll dist = time_stamp[p][q][r], cyc_len = time_stamp[temp][p][q] - time_stamp[p][q][r] + 1;
    if(K > dist){
        K -= dist;
        K %= cyc_len;
        K += dist;
    }
    int ans;
    for(int i = 0; i < 10; i++){
        for(int j = 0; j < 10; j++){
            for(int k= 0; k < 10; k++){
                if(K == time_stamp[i][j][k]){
                    ans = cyc[i][j][k];
                    break;
                }
            }
        }
    }
    cout << ans << endl;
}