def main():
    p, q, r, K = map(int, input().split())

    memory = [[[-1 for _ in range(10)] for _ in range(10)] for _ in range(10)]

    p, q, r = p % 10, q % 10, r % 10
    memory[p][q][r] = 3
    for ctr in range(4, K+1):
        p, q, r = q, r, (p+q+r) % 10
        if memory[p][q][r] == -1:
            memory[p][q][r] = ctr
            continue

        rest = (K - ctr) % (ctr - memory[p][q][r])
        for p_idx, qr_elms in enumerate(memory):
            for q_idx, r_elms in enumerate(qr_elms):
                for r_idx, memory_ctr in enumerate(r_elms):
                    if memory_ctr == memory[p][q][r] + rest:
                        print(r_idx)
                        return
    print(r)


if __name__ == "__main__":
    main()