It's strange you get the right answer in your IDE and not here. It would mean the C implementations differ, some difference in the compiler... I'm not an expert so I can't say for sure but I don't even know if that's possible. I guess there must be some difference somewhere (a variable with a different type or something like that). So I would suggest first to double check that, and also have a look here: Troubleshooting Your Solution. After checking it if you cannot find the problem you may post your code with a spoiler flag and someone may help you (with no guarantee). There are many ways to solve this kata so it's hard to help without more informations.

Language?