Story

I just participated as an unrated contestant in Educational Codeforces Round 88 (Rated for Div. 2). I was trying hard to solve problem C, yet keep getting WA on test 4. I didn't solve the problem in during the contest, and when I was testing my solutions after the contest, something weird happens.

Check this out

Compiler : C++17 AC

Compiler : C++17 (64bit) WA

I know nothing about the compiler.

I am just curious about what causes this difference, and what should I do to avoid these bugs.