if input is chars = ["a","a","b","b","c","c","c"] output should be output = ["a","2","b","2","c","3"] and if the input is like chars = ["a","b","b","c","c","c"] output should be output = ["a","b","2","c","3"] and if the input is like chars = ["a","b","b","c","c","c","c","c","c","c","c","c","c","c","c"] output should be output = ["a","b","2","c","1","2"]...do not use any data structures
