405050: GYM101755 C Third-Party Software

Pavel is developing a game. To do that, he needs functions available in a third-party library too famous to be called. It is known that the function i first appeared in version a_i and existed until version b_i, and starting from the version b_i + 1, it is absent in this library.

The library is not free and Pavel needs all the functions. Which minimal number of versions he need to purchase to be able to use all the functions?

The first line contains a single integer n (1 ≤ n ≤ 200000) — the number of the functions.

Each of the next n lines contains two integers a_i and b_i (1 ≤ a_i ≤ b_i ≤ 10⁹) — the interval of library versions where function i was available.

In the first line output a single integer k — the minimal number of library versions need to be purchased to unlock all functions.

In the second line output k distinct integers — the numbers of versions need to be purchased.

If there are several possible answers, output any of them.

5
2 4
1 3
2 3
3 6
4 5

2
3 4