import collections
from itertools import count

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

p %= 10
q %= 10
r %= 10
memo = collections.defaultdict(int)
memo[p, q, r] = 3
a = [p, q, r]
for i in count(4):
    x = (a[-1] + a[-2] + a[-3]) % 10
    a.append(x)
    if i == K:
        print(a[-1])
        break

    key = (a[-3], a[-2], a[-1])
    if key in memo: # found cycle
        m = memo[key]
        t = K - (m - 1)
        d = i - m
        index = t % (i - m)
        print(a[index + 1])
        # print(f'{index=}')
        # print(f'{a=}')
        break

    memo[key] = i
    if i == K:
        print(a[-1])
        break