#include <iostream>
#include <string>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <vector>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <list>
#include <iterator>
#include <cassert>
#include <numeric>
#include <functional>
#include <ctime>
#include <bitset>
#pragma warning(disable:4996) 

//#define ATCODER
#ifdef ATCODER
#include <atcoder/all>
#endif

typedef long long ll;
typedef unsigned long long ull;
#define LINF  9223300000000000000
#define LINF2 1223300000000000000
#define LINF3 1000000000000
#define INF 2140000000
//const long long MOD = 1000000007;
const long long MOD = 998244353;

using namespace std;
#ifdef ATCODER
using namespace atcoder;
#endif



void solve()
{
    vector<int> a(1005); ll K;
    scanf("%d%d%d%lld", &a[0], &a[1], &a[2], &K); K--;
    a[0] %= 10; a[1] %= 10; a[2] %= 10;

    int id0 = -1, id1 = -1;
    vector<int> f(1000, -1);
    for (int i = 0; i <= 1000; i++) {
        int tmp = a[i] * 100 + a[i + 1] * 10 + a[i + 2];
        a[i + 3] = (a[i] + a[i + 1] + a[i + 2]) % 10;

        if (f[tmp] < 0) {
            f[tmp] = i;
        }
        else {
            id0 = f[tmp]; id1 = i; break;
        }
    }
    assert(id0 >= 0 && id1 >= 0);

    if (K < id1) {
        printf("%d\n", a[(int)K]);
    }
    else {
        int m = id1 - id0;
        int d = (K - id1) % m;
        printf("%d\n", a[id0 + d]);
    }


    return;
}

int main()
{
#if 1
    solve();
#else
    int T, t;
    scanf("%d", &T);
    for (t = 0; t < T; t++) {
        //printf("Case #%d: ", t + 1);
        solve();
    }
#endif
    return 0;
}