You have an array that contains a permutation of integers $1,2,\dots,n$ . Your task is to sort the array in increasing order by reversing subarrays. You can construct any solution that has at most $n$ reversals.
The first input line has an integer $n$ : the size of the array. The array elements are numbered $1,2,\dots,n$ .
The next line has $n$ integers $x_1,x_2,\dots,x_n$ : the contents of the array.
First print an integer $k$ : the number of reversals.
After that, print $k$ lines that describe the reversals. Each line has two integers $a$ and $b$ : you reverse a subarray from position $a$ to position $b$ .