403387: GYM101149 B No Time for Dragons

One fairy king hated dragons to death. Not only that these monsters burn whole villages to ashes, kidnap princesses and guard treasures that they don't need at all, but they are also mentioned in statements of programming problems very often. To end their tyranny, he decided to recruit an army and destroy these damned creatures once and forever.

The king found out that there are n dragons in total, and to defeat the i-th of them he needs an army of a_i soldiers, b_i of which will be killed during the battle. Now he wants to know the minimal number of soldiers he needs to recruit in order to kill all the dragons. The king doesn't care about the order of battles: the only thing that matters is that none of the dragons will be left alive.

The first line contains a single integer n (1 ≤ n ≤ 2·10⁵) — the number of dragons.

Each of the next n lines contains two space-separated integers: a_i and b_i (1 ≤ b_i ≤ a_i ≤ 10⁹) — the number of soldiers needed to defeat the i-th dragon, and the number of soldiers that will be killed in the battle against him.

Output a single integer — the minimal number of soldiers that is sufficient to kill all the dragons.

2
7 4
5 1

8

3
4 1
6 4
5 3

10