Hello everyone. Recently I've explored a better solution O(N*logN) instead of O(N^2) for 13C (Sequences) using Priority Queue: https://codeforces.com/contest/13/submission/94130902. But I can't understand why it is work. Can somebody explain the main idea of O(N*logN) solution for me? Thanks so much.

Can someone help me in this problem please? I debugged it for a while but I can't understand why my code was being MLE :(( Thank you so much. P/S: Sorry for my bad English :( Sub: https://codeforces.com/contest/769/submission/93610574