B"You are given n pairs of integers (a_1, b_1), (a_2, b_2), ldots, (a_n, b_n) . All of the integers in the pairs are distinct and are in the range from 1 to 2 cdot n inclusive. Let's call a sequence of integers x_1, x_2, ldots, x_{2k} good if either You need to choose a subset of distinct indices i_1, i_2, ldots, i_t and their order in a way that if you write down all numbers from the pairs in a single sequence (the sequence would be a_{i_1}, b_{i_1}, a_{i_2}, b_{i_2}, ldots, a_{i_t}, b_{i_t} ), this sequence is good. What is the largest subset of indices you can choose? You also need to construct the corresponding index sequence i_1, i_2, ldots, i_t . The first line contains single integer n ( 2 <= q n <= q 3 cdot 10^5 ) -- the number of pairs. Each of the next n lines contain two numbers -- a_i and b_i ( 1 <= a_i, b_i <= 2 cdot n ) -- the elements of the pairs. It is guaranteed that all integers in the pairs are distinct, that is, every integer from 1 to 2 cdot n is mentioned exactly once. In the first line print a single integer t -- the number of pairs in the answer. Then print t distinct integers i_1, i_2, ldots, i_t -- the indexes of pairs in the corresponding order. The final sequence in the first example is 1 < 7 > 3 < 5 > 2 < 10 . The final sequence in the second example is 6 > 1 < 3 > 2 < 5 > 4 . "...