from collections import deque

p,q,r,K = map(int,input().split())
p,q,r = int(str(p)[-1]),int(str(q)[-1]),int(str(r)[-1])
check = [[[0]*10 for _ in range(10)] for _ in range(10)]
check[p][q][r] = 3
memo = [p,q,r]
count = 3
l = deque([p,q,r])
while count < K:
  count += 1
  num = sum(l)
  num = int(str(num)[-1])
  l.popleft()
  l.append(num)
  memo.append(num)
  i,j,k = l[0],l[1],l[2]
  if check[i][j][k] > 0:
    turn = count-check[i][j][k]
    K %= turn
    ans = memo[check[i][j][k]+K-4]
    print(ans)
    exit()
  check[i][j][k] = count

print(memo[-1])