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

A = [0] * 1001
A[1] = p
A[2] = q
A[3] = r
memo = [0] * 1000
memo[p * 100 + q * 10 + r] = 3

i = 4
while True:
    A[i] = A[i-1] + A[i-2] + A[i-3]
    A[i] %= 10
    u = A[i] * 100 + A[i-1] * 10 + A[i-2]
    if memo[u]:
        loop = i - memo[u]
        start = memo[u]
        break
    else:
        memo[u] = i
    i += 1
if K <= start:print(A[K])
else:
    r = (K - start) % loop
    print(A[start+r])