stylesheet - How to change size of all inputs?

I would like to change the font size of inputs and outputs. I see that I can just click on options of every single input and set the size, but I don't want to do this separately for every line. Could someone help me find options to do it?

Edit:

I discovered that I can check one Input cell with Alt and then use Alt+- to resize it, too.

Answer

You can edit the StyleSheet to change the font sizes of "Input" and "Output" cells. Adapting @MichaelE2's answer in this related Q/A: Change font of formula number in DisplayFormulaNumbered