3.12Harmonic minor has a strange interval

A harmonic minor:

A B C D E F G♯ A

Between:

F → G♯

there are 3 semitones.

That's called an augmented second.

It gives harmonic minor its distinctive sound.

Play:

F → G♯ → A

You'll probably immediately hear a somewhat exotic or dramatic quality.

Historically, that awkward melodic gap is one reason melodic minor evolved as another solution.