n = int(input())
p = list(map(int,input().split()))
ans = 1
for i in p:
    ans *= i

now = 0
ans = str(ans)
for i in ans:
    now += int(i)
    if now == 10:
        now = 1
    elif now == 11:
        now = 2
    elif now ==12:
        now = 3
    elif now ==13:
        now = 4
    elif now ==14:
        now =5
    elif now ==15:
        now = 6
    elif now ==16:
        now = 7
    elif now == 17:
        now = 8
    elif now ==18:
        now = 9
    elif now ==19:
        now = 1
            
print(now)