Correct output with 'run code', but Private test results shows wrong actual output. 

This is the first question in Strings. When I run the code in the run code window, I get the desired output. But Private test 1 seems to consider a wrong 'actual output'. I have run this code in other IDEs and the results are correct. How do I resolve this?

You are given a number with duplicate digits your task is to remove the immediate duplicate digits and print the result

Input Description:
You are given a long string of digits

Output Description:
Print the desired result print -1 if result length is 0

Sample Input :
1331

Sample Output :
11