I'm unable to solve Problem C (Gary) of Codeforces Training Season 3 Episode 9. The contest is available on Gym. Link: http://codeforces.com/gym/101156.

Can someone please help me in solving this problem!!

After the contest, my submission got RunTime Error on Test Case #17. Link:- http://codeforces.com/contest/707/submission/19991308

I couldnt figure out my mistake. I tried making a few changes and finally got an AC. Link:- http://codeforces.com/contest/707/submission/20084074

The only difference is in the compare function. I still didnt understand why did my first code get a Run Time error. Please help me to understand what went wrong.