import sys; input = sys.stdin.buffer.readline
sys.setrecursionlimit(10**7)
from collections import defaultdict
con = 10 ** 9 + 7; INF = float("inf")

def getlist():
	return list(map(int, input().split()))

#処理内容
def main():
	N = int(input())
	P = getlist()
	v = 1
	for i in P:
		v *= i

	while True:
		if v <= 9:
			print(v)
			return

		v = sum(list(map(int, list(str(v)))))


if __name__ == '__main__':
	main()