def s(n):
    x = 0
    z = str(n)
    y = len(z)
    for i in range(y):
        x += n//(10**(y-i-1))
        n -= (n//(10**(y-i-1)))*10**(y-i-1)
    return(int(x))  
    
    
n = int(input())
s = input().split()
x = []
for i in s:
    x.append(int(i))
ans = 1
for i in x:
    ans *= i
while ans>9:
    ans = sum(list(map(int, str(ans))))
print(ans)