from functools import reduce
from operator import mul
from sys import stdin


def main():
    input = lambda: stdin.readline()[:-1]
    N = int(input())
    P = map(int, input().split())

    k = reduce(mul, P)
    ans, d = 0, 1
    while 1:
        while d > 0:
            d, m = divmod(k, 10)
            ans += m
            k = d
        if ans < 10:
            break
        d, k = 1, ans
        ans = 0
    print(ans)


main()