#include <bits/stdc++.h>
template<class T> inline bool chmin(T&a, T b){if(a > b){a = b; return true;}else{return false;}}
template<class T> inline bool chmax(T&a, T b){if(a < b){a = b; return true;}else{return false;}}
#define ll long long
#define double long double
#define rep(i,n) for(int i=0;i<(n);i++)
#define REP(i,n) for(int i=1;i<=(n);i++)
#define mod (ll)(1e9+7)
#define inf (ll)(3e18+7)
#define eps (double)(1e-9)
#define pi (double) acos(-1)
#define all(x) x.begin(),x.end()
#define rall(x) x.rbegin(),x.rend()
using namespace std;

struct ary{
    int a, b, c;
};

ll p, q, r, k;

ary tri(int x, int y, int z){
    ary ret;
    ret.a = x;
    ret.b = y;
    ret.c = z;
    return ret;
}

int main(){
    cin >> p >> q >> r >> k;
    k-=3;
    bool visited[10][10][10];
    memset(visited, false, sizeof(visited));
    vector<ary> loop;
    loop.push_back(tri(p%10, q%10, r%10));
    visited[p%10][q%10][r%10] = true;
    while(true){
        int x = loop.back().a;
        int y = loop.back().b;
        int z = loop.back().c;
        loop.push_back(tri(y, z, (x+y+z)%10));
        if(visited[y][z][(x+y+z)%10])break;
        visited[y][z][(x+y+z)%10] = true;
    }
    if(k < (int)loop.size()){
        cout << loop[k].c << endl;
        return 0;
    }
    k -= loop.size() - 1;
    p = loop.back().a;
    q = loop.back().b;
    r = loop.back().c;
    memset(visited, false, sizeof(visited));
    loop.clear();
    loop.push_back(tri(p%10, q%10, r%10));
    visited[p%10][q%10][r%10] = true;
    while(true){
        int x = loop.back().a;
        int y = loop.back().b;
        int z = loop.back().c;
        if(visited[y][z][(x+y+z)%10])break;
        loop.push_back(tri(y, z, (x+y+z)%10));
        visited[y][z][(x+y+z)%10] = true;
    }
    k %= (int)loop.size();
    cout << loop[k].c << endl;
}