I've lost count of how many times I've received an email from a random headhunter asking me to participate in their hiring process. I accepted one and was interviewed remotely. I passed, and then they scheduled the technical interview. They shared a problem with me, and I was able to solve it. It worked as expected, and the interviewer congratulated me, saying it was a good solution. We then discussed the problem further. Afterwards, I received feedback stating I did not pass the hiring process. I don't know why, but that's how it is. At least I've stopped receiving too many emails from headhunters :)

Solve this problem given an input and output.