c# - How to manipulate a int by pressing two digits on the numpad?

Hello everyone, i am relatively new to unity so i think this might be a pretty basic question. i have a value between 0 and 50. it is defined as an int. i want to manipulate that value by pressing two digits on the numpad in sequence, so for example if i click on 3 and then on 5, the value should be 35 or if i click 0 and 8 the value should be 8. i have no clue how to handle these sequences and form an int out of the two keys. I am happy about any kind of help. Thanks in advance