import sys
input=lambda: sys.stdin.readline().rstrip()
n=int(input())
P=[int(i) for i in input().split()]
def tot(x):
  while x>=10:
    res=0
    for xx in str(x):
      res+=int(xx)
    x=res
  return x
ans=1
for p in P:
  ans=tot(ans*p)
print(ans)