import math
import sys
def S(): return sys.stdin.readline().rstrip()
def I(): return int(sys.stdin.readline().rstrip())
def MI(): return map(int, sys.stdin.readline().rstrip().split())
def LI(): return list(map(int, sys.stdin.readline().rstrip().split()))
def LS(): return list(sys.stdin.readline().rstrip().split())

n = I()
p = LI()

ans = 1
for i in p:
    ans *= i

while ans > 9:
    s = list(str(ans))
    s = list(map(int, s))
    ans = sum(s)

print(ans)