#pragma region Macros

#include <bits/extc++.h>
using namespace std;
using namespace __gnu_pbds;
// using namespace __gnu_cxx;

#define TO_STRING(var) # var
#define pb emplace_back
#define int ll
#define endl '\n'

using ll = long long;
using ld = long double;
const ld PI = acos(-1);
const ld EPS = 1e-10;
const int INF = 1 << 30;
const ll INFL = 1LL << 62;
// const int MOD = 998244353;
const int MOD = 1000000007;

int ceil(int x, int y) {return (x > 0 ? (x + y - 1) / y : x / y);}
int POW(int x, int y) {
    if (y != (int)(y) or y < 0 or x != 0 && x != 1 && y > 64) {cout << "Error" << endl;return 0;}
    if (y == 0) return 1;
    if (y % 2 == 0) return POW(x * x, y / 2);
    return x * POW(x, y - 1);
}

__attribute__((constructor))
void constructor() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << fixed << setprecision(15);
}

#pragma endregion

signed main(){
	int p, q, r, K;
	cin >> p >> q >> r >> K;
	p %= 10; q %= 10; r %= 10;

    vector<int> trib(10000);
    trib[0] = p;
    trib[1] = q;
    trib[2] = r;

    int len = 0;
	for (int i = 3; i < 10000; i++) {
        trib[i] = trib[i - 1] + trib[i - 2] + trib[i - 3];
        trib[i] %= 10;
		if (trib[i] == r && trib[i - 1] == q && trib[i - 2] == p) {
			len = i - 2;
			break;
		}
    }

	cout << trib[K % len - 1] << endl;
}