Compute and generate a compressed string for a given string containing repetitions
For a given string return a compressed string which replaces all the repetitions of the characters with their counts. If the compressed string is not smaller than the initial string return the original string as it is. For example, if the input string is "aabbbbbcccdddeef", then the resultant string should be "a2b5c3d3e2f1", whereas if the input string is "abcdef" then the output should be "abcdef".