import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int p = Integer.parseInt(sc.next()) % 10;
		int q = Integer.parseInt(sc.next()) % 10;
		int r = Integer.parseInt(sc.next()) % 10;
		long K = Long.parseLong(sc.next());
		sc.close();
		
		long[] cnt = new long[1000];
		long i = 3;
		long ans = 0;
		while ( true ) {
			if ( i == K ) {
				ans = r;
				break;
			}
			if ( cnt[100 * p + 10 * q + r] > 0 ) {
				long per = i - cnt[100 * p + 10 * q + r];
				long x = (K - i) / per;
				i += x * per;
				i++;
				for ( ; i <= K ; i++ ) {
					int n = (p + q + r) % 10;
					p = q;
					q = r;
					r = n;
				}
				ans = r;
				break;
			} else {
				cnt[100 * p + 10 * q + r] = i++;
			}
			int n = (p + q + r) % 10;
			p = q;
			q = r;
			r = n;
		}

		System.out.println(ans);
	}
}