import numpy as np
p, q, r, K = map(int, input().split())

xs = [[1,1,1],[1,2,2],[2,3,4]]
X = np.array(xs, dtype="object")
S = np.array([p,q,r], dtype="object")
K,m=divmod(K,3)
for _ in range(60):
    if K%2:
        S = np.dot(X, S)%10
    K = K//2
    X = np.dot(X, X)%10
S = np.array(S, dtype="int64")
print(S[(m-1)%3])