Sort from 0 to n - 1

Given a sequence of numbers $a_0,a_1,...a_{n-1}$ consisting of $n$ unique elements, each of which belongs to the range $[0;n-1]$. A swap is defined as an operation $(i,j)(0\le i,j\le n-1)$ that exchanges the values of $a_i$ and $a_j$. Sort the sequence using the minimum number of swaps. Print all the swaps performed.

Input

The first line contains a positive integer $n(n\le 10^6)$. The second line contains $n$ distinct numbers from the range $[0;n-1]$.

Output

In the first line print the minimum number of performed swaps $k$. In the next $k$ lines print all the swaps in the form of pairs $(i,j)$.

Examples