Today is pretty much like another day, I choose to grind some codeforces problem here and there... I choose to solve this problem today: Grid XOR

It so happens I wrote a solution and tested on local, works perfectly fine. But when I submitted OJ tell me it's runtime error on test 1 (?)

This never happened to me before so I'm confused. So I happen to submitted mutliple bad subs to test what actually happened, and this is what I've found: Compared this 2 submission: 314967876 vs 314969708

The only difference is this line of code, and it causes RTE:

input = io.BytesIO(os.read(0, os.fstat(0).st_size)).readline

What happened to python fastIO input? Just pretty much yesterday everything works fine and now it doesn't? I tried to scramble blogs updated from yesterday till today and found nothing.

Can anyone fill me up what's happening?