Given a string S and an integer K, the task is to reduce the string by applying the following operation:
Choose a group of K consecutive identical characters and remove them. The operation can be performed any number of times until it is no longer possible

One string which is S and one integer which is K  (You can assume all lower case letters)
1<= |S| <= 1000,000
1<= K <= |S|

The final string. (if it is empty string, just output "DELETE ALL" )