Error when running but no error on submission

[ssjgz]

Are you clicking “Run” without providing custom input?

New to Codechef. Can't understand the platform

One thing that trips up all people migrating from Hackerrank (hello :)) is that clicking “Run” (not “Submit”) here on Codechef does not run your code with the sample testcases - instead, it runs it with empty input (so attempts to read anything from stdin will fail, or give weird values). If you click “Run”, you must provide Custom Input.