Read text file content to determine which level to load

hi there
i have a script that creates a text file with a number written in it, like a 1 or a 2, what i need is a script that reads the file and if there is a 1 the game should load the level 1 scene, if there is a 2 then load level 2, a 3 to load level 3…

how can i do this?