x = 1
n = gets.to_i
a = gets.chomp.split(" ")
for i in 0..n-1
  x *= a[i].to_i
  while x>=10 and x%10==0
    x/=10
  end
end

y = 0
while x>0
  y+=x%10
  if y>=10
    y = y/10 + y%10
  end
  x/=10
end
print y