from itertools import count


def cycle_detection(k, inits, fnext):
    memo = {}
    memo[inits[0], inits[1], inits[2]] = 2
    a = inits[:]
    for i in count(len(inits)):
        x = fnext(a)
        a.append(x)
        if i == k:
            return x

        key = (a[-3], a[-2], a[-1])
        if key in memo: # found cycle
            loop_start = memo[key]
            loop_len = i - loop_start
            index = (k - loop_start) % loop_len + loop_start
            return a[index]
        memo[x] = i


p, q, r, K = map(int, input().split())
p %= 10
q %= 10
r %= 10


def fnext(a):
    return (a[-1] + a[-2] + a[-3]) % 10


ans = cycle_detection(K-1, [p, q, r], fnext)
print(ans)