A9222 | Permutation

A permutation $p$ is an ordered group of numbers $p_{1},p_{2},...,p_{n}$ , consisting of $n$ distinct positive integers, each is no more than $n$ . We'll define number $n$ as the length of permutation $p_{1},p_{2},...,p_{n}$ .

Simon has a positive integer $n$ and a non-negative integer $k$ , such that $2k<=n$ . Help him find permutation $a$ of length $2n$ , such that it meets this equation: .

The first line contains two integers $n$ and $k$ ( $1<=n<=50000$ , $0<=2k<=n$ ).

Print $2n$ integers $a_{1},a_{2},...,a_{2n}$ — the required permutation $a$ . It is guaranteed that the solution exists. If there are multiple solutions, you can print any of them.