How can white mate black in 4 moves? In this endgame position, how can black be mated in 4 moves? Being a beginner, I am finding it difficult

[FEN "8/8/6R1/8/8/4K2p/7k/8 w - - 0 1"]
Use the king to keep the black king in the corner and force Black into zugzwang:

[FEN "8/8/6R1/8/8/4K2p/7k/8 w - - 0 1"]

1.Kf2 Kh1 2. Re6 Kh2 (2... h2 3. Re1) 3. Rh6 Kh1 4.Rxh3