B'There are n coins labeled from 1 to n . Initially, coin c_i is on position i and is facing upwards (( c_1, c_2, ... , c_n) is a permutation of numbers from 1 to n ). You can do some operations on these coins. In one operation, you can do the following: Choose 2 distinct indices i and j . Then, swap the coins on positions i and j . Then, flip both coins on positions i and j . (If they are initially faced up, they will be faced down after the operation and vice versa) Construct a sequence of at most n+1 operations such that after performing all these operations the coin i will be on position i at the end, facing up. Note that you do not need to minimize the number of operations. The first line contains an integer n ( 3 <= q n <= q 2 cdot 10^5 ) -- the number of coins. The second line contains n integers c_1,c_2, ... ,c_n ( 1 <= c_i <= n , c_i neq c_j for i neq j ). In the first line, output an integer q (0 <= q q <= q n+1) -- the number of operations you used. In the following q lines, output two integers i and j (1 <= q i, j <= q n, i ne j) -- the positions you chose for the current operation. Let coin i facing upwards be denoted as i and coin i facing downwards be denoted as -i . The series of moves performed in the first sample changes the coins as such: In the second sample, the coins are already in their correct positions so there is no need to swap. '...