Same code got TLE in GNU C++11 and got AC in GNU C++17. Can someone please tell me the reason behind it?

TLE (C++11): http://codeforces.net/contest/1520/submission/115347126

AC (C++17): http://codeforces.net/contest/1520/submission/115347176

Thanks!

It's been more than 1 hour and my last two submissions are still in queue when I write this blog. Is there any problem with judging? My submissions: 80013286 80013219

Please help me. Thanks.

Initially I use GNU C++17 when I submit codes. I submitted code for 235A — LCM Challenge and got WA on test 61 using GNU C++17. Then again I submitted the same code in GNU C++14 and got Accepted. My submissions are here,

GNU C++17: 78659557 (Wrong answer on test 61)

GNU C++14: 78659665 (Accepted)

I found no explanation of it and thinking about what if it happened in contest time. Can you suggest me any reason? Thank you so much!