N = int(input())
P = list(map(int,input().split()))

MOD = 10**9+7
K = 1

for p in P:
  K *= p


l = list(str(K))
ans = 0

for k in l:
  ans += int(k)
while len(str(ans)) > 1:
  count = 0
  l = list(str(ans))
  for k in l:
    count += int(k)
  ans = count
print(ans)