from collections import defaultdict
p,q,r,K = list(map(int,input().split()))

now = (p+q+r) % 10
A = [p,q,r]
d = defaultdict(int)
for i in range(4,K+1):
    now = (A[-1] + A[-2] + A[-3]) % 10
    A.append(now)
    if(now not in d):
        d[now] = i
    else:
        loop_len = i - d[now]
        nokori = (K - i) % loop_len
        for _ in range(nokori):
            now = (A[-1] + A[-2] + A[-3]) % 10
            A.append(now)
        print(now)
        exit()
print(now)