String Changes

Have the function stringchanges $($str$)$ take the stx parameter being passed, which will be a string containing letters from the alphabet, and return a new string based on the following rules. Whenever a capital $M$ is encountered, duplicate the previous character $($then remove the M$),$ and whenever a capital $N$ is encountered remove the next character from the string $($then remove the N$).$ All other characters in the string will be lowercase letters. For example: "abcNdgM" should return "abcgg". The final string will never de empty.

Examples