import numpy as np

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

K -= 3
A = np.array([[1, 1, 1], [1, 0, 0], [0, 1, 0]])
A % 10
l = np.array([r, q, p])

R = 0

for i in range(60):
    if (K >> i) & 1 == 1:
        l = A @ l
        l = l % 10

    A = A @ A
    A = A % 10

print(l[0] % 10)