import sys

sys.setrecursionlimit(10 ** 6)
int1 = lambda x: int(x) - 1
p2D = lambda x: print(*x, sep="\n")
def MI(): return map(int, sys.stdin.readline().split())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]

def sum_dig(x):
    res=0
    while x>0:
        x,r=divmod(x,10)
        res+=r
    return res

def main():
    n=int(input())
    pp=LI()
    s=1
    for p in pp:
        s=sum_dig(s*p)
        while s>10:
            s=sum_dig(s)
    print(s)

main()