P5918 [FJOI2015] Coin Swapping Problem

Given an integer $n$, the initial sequence looks like this: $$ \underbrace{\tt 111\cdots11}_{n \text{ ones}}\underbrace{\tt 000\cdots00}_{n \text{ zeros}}\verb!__! $$ Now you need to use the minimum number of swaps to make the final sequence become: $$ \underbrace{\tt 101010\cdots 1010}_{2\times n \text{ digits with alternating } 0 \text{ and } 1}\verb!__! $$ A swap means **moving two adjacent non-blank digits together onto the two blanks**. For example, the following is a valid solution when $n=4$: - Initial state: $\verb!11110000__!$. - Step $1$: $\verb!__11000011!$. - Step $2$: $\verb!101__00011!$. - Step $3$: $\verb!1010100__1!$. - Step $4$: $\verb!10101__001!$. - Step $5$: $\verb!10101010__!$. It can be proven that the minimum number of operations is $5$.

The input contains one line with an integer $n$.

Output the minimum number of moves in the first line. In the next line, output a move plan. You only need to output the index of the left one of the two moved non-blank cells. See the sample for details.

For $100\%$ of the testdata, $2