CSES - Reversal Sorting
  • Time limit: 1.00 s
  • Memory limit: 512 MB
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.

Input

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.

Output

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 $b$.

Constraints
  • $1 \le n \le 2 \cdot 10^5$
Example

Input:
4
2 3 1 4


Output:
2
1 3
2 3