You have to create a function,named `insertMissingLetters`, that takes in a `string` and outputs the same string processed in a particular way.

The function should insert **only after the first occurrence** of each character of the input string, all the **alphabet letters** that:

-**are NOT** in the original string  
-**come after** the letter of the string you are processing  

Each added letter should be in `uppercase`, the letters of the original string will always be in `lowercase`.


Example:  


`input`: "holly"  

`missing letters`: "a,b,c,d,e,f,g,i,j,k,m,n,p,q,r,s,t,u,v,w,x,z"  

`output`: "hIJKMNPQRSTUVWXZoPQRSTUVWXZlMNPQRSTUVWXZlyZ"  


You don't need to validate input, the input string will always contain a certain amount of lowercase letters  (min 1 / max 50).