This app let the user to enter an input based on the options chosen from the Checkbox. For checking the constraints regular expression has been used to simply and make the code easy.
Some screenshots of the app is attached below and the app APK could be found at the last.
Download APK from here : https://github.com/shubh3483/Input-Constraints/releases/download/v5.5.3/Input-Constraints1.apk