#B AC 31 min 1 wrong try by WHD
#A AC 50 min by WDP
#D AC 75 min 3 wrong tries by WHD
#G AC 79 min 5 wrong tries
It can be solved by brute force, but I used DP to solve it, so I wasted a lot of time.
#C AC 94 min 1 wrong try
For a query, if b>sqrt(n), we can response it by brute force.
After do some preparations in O(n^1.5), we can response qeuries whose b<=sqrt(n) in O(1).
#F AC 118 min 1 wrong try by WHD
#E AC 179 min by WDP