Hi Codeforces,

We saw an unusual amount of hacks today. Specifically, there were a lot of hacks on problem B, I did one myself. The submission I hacked looked like this

t = int(input().strip())
for _ in range(t):
    n = int(input().strip())
    s = str(n)
    sz = len(s)
    
    sm = "01234"
    lr = "56789"
    if sm in s and lr in s:
        print("No")
        break
    
    flag = False
    total_sum = 0
    arr = [5, 6, 7, 8, 9]
    for i in range(sz - 1):
        total_sum += int(s[i])
        if s[i] == '0':
            flag = True
    
    if s[-1] == '9':
        print("No")
    elif total_sum == 35:
        print("No")
    elif s[0] != '1':
        print("No")
    elif sz % 10 == 0:
        print("No")
    elif flag:
        print("No")
    else:
        print("Yes")

As you can see, it's a completely valid solution except there are 2 unnecessary if statements which made it hackable. That made me think of 2 things: why there wasn't any 10-digit number in pretests and why the contestant wrote that "if"?

But after the contest I saw a list of hacks and, to my surprise, there were A LOT of hacks on similar submissions. So my hypothesis is that one of the authors intentionally spread an incorrect solution in some cheating community and removed all 10digit numbers from pretests. If that's true, I pay my respect