n=int(input())
v=1
a=list(map(int,input().split()))
for i in range(n):
  v*=a[i]
while True:
  v_s=str(v)
  tmp=0
  for i in range(len(v_s)):
    tmp+=int(v_s[i])
  if tmp<10:
    break
  else:
    v=tmp
print(tmp)