import sys
sys.set_int_max_str_digits(0)

def d(x):
	res=0
	for i in range(len(x)):
		res+=int(x[i])
	return res

n=int(input())
x=list(map(int,input().split()))
y=1
for k in x:
	y*=k
y=str(y)
while len(y)!=1:
	y=str(d(y))
print(y)