Be careful

Sergey knows many programming languages and particularly enjoys experimenting with new approaches, syntax, and coding styles. Because of this, he often switches between different languages even within a single day: in the morning he might write in Python, in the afternoon solve a problem in C++, and in the evening try his hand at Rust or JavaScript.

Once, Sergey was working on a problem to submit for review. He read the problem statement carefully, thought through a solution, quickly sat down to write the code, and got so absorbed in the process that he didn’t even notice one small detail. Only when everything was already finished did Sergey realize with surprise that he had written the program in a completely different language than the one he intended to submit it in.