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

A = {}
A[0] = p % 10
A[1] = q % 10
A[2] = r % 10


def conv(a, b, c):
    return (a % 10) * 100 + (b % 10) * 10 + c % 10


t = set()
t.add(conv(A[0], A[1], A[2]))
for k in range(3, 1000):
    A[k] = (A[k - 1] + A[k - 2] + A[k - 3]) % 10
    t.add(conv(A[k], A[k - 1], A[k - 2]))

print(A[(K - 1) % (len(t) - 1)])