Question is: https://www.codechef.com/problems/BOMBING?tab=statement submission: https://www.codechef.com/viewsolution/1035044414 approach I was thinking solving with pref of array and (segment tree) that is counting the current open system and minus with count of all system having end less me and start greater than me and as element can be equal iam only updating there first occurrence count that resolve the things but still not accepting anyone can tell what the issue along with anyone similar question on codeforces. ( similar to codeforces 61E (https://codeforces.net/problemset/problem/61/e )