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())

    def func(n):
        ret, d = 0, 1
        while d > 0:
            d, m = divmod(n, 10)
            ret += m
            n = d
        return ret

    p = [func(i) for i in P]
    k = reduce(mul, p)
    ans = 10
    while ans > 9:
        ans = func(k)
        k = ans
    print(ans)


main()