// 問題の URL を書いておく
// 

#include <bits/stdc++.h>

using namespace std;

#define ENABLE_PRINT

#if defined(ENABLE_PRINT)

#define Print(v) \
do {\
    cerr << #v << ": " << v << endl; \
}while(0)

#define PrintVec(v) \
do {\
    for(int __i = 0; __i < v.size(); ++__i) \
    { \
        cerr << #v << "[" << __i << "]: " << v[__i] << endl; \
    }\
}while(0)

#define P(fmt, ...) fprintf(stderr, fmt, __VA_ARGS__)
#define LP fprintf(stderr, "L: %d\n", __LINE__)

#else

#define Print(v) ((void)0)
#define PrintVec(v) ((void)0)
#define P(fmt, ...) ((void)0)
#define LP ((void)0)

#endif

#define rep(i, n) for(int i = 0; i < (int)(n); ++i)

using ll = long long;

int moves[10][10][10];
int moved[10][10][10];

int main(int, const char**)
{
    rep(i, 10) rep(j, 10) rep(k, 10)
    {
        moves[i][j][k] = (i + j + k) % 10;
        moved[i][j][k] = -1;
    }

    int p, q, r;
    ll K;
    cin >> p >> q >> r >> K;
    p %= 10; q %= 10; r %= 10;

    int t = 0;
    vector<int> ans;
    while(true)
    {
        if(moved[p][q][r] != -1)
        {
            break;
        }
        moved[p][q][r] = t++;
        auto nx = moves[p][q][r];
        ans.push_back(nx);
        p = q;
        q = r;
        r = nx;
    }

    auto clen = t - moved[p][q][r];
    auto plen = moved[p][q][r];
    P("clen: %d\n", clen);
    P("plen: %d\n", plen);

    P("-----\n", 0);
    rep(i, (int)ans.size())
    {
        P("%d: %d\n", i, ans[i]);
    }
    K -= 4;
    if(K < plen)
    {
        cout << ans[K] << endl;
    }
    else
    {
        auto rest = K - plen;
        auto m = rest % clen;
        cout << ans[plen + m] << endl;
    }
    return 0;
}