Guys , I need an aircond for my house , too hot with recent temp. Below are the details

Cooling area living room. 24× 21feet x13 feet ceiling. The problem is in the middle of the living room is the stairs to 2nd floor.

So should I install the aircond on the wall of the stairs so cold air can blow to living room or install at living room ? How many hp and inverter or non inverter ? Normally I will use during night 5 hrs only.thanks