package main

import (
	"bufio"
	"fmt"
	"os"
	"strconv"
)

func main() {
	scanner := bufio.NewScanner(os.Stdin)
	scanner.Split(bufio.ScanWords)
	buf := make([]byte, 1024*1024)
	scanner.Buffer(buf, 1024*1024)

	scanInt := func() int {
		scanner.Scan()
		res, _ := strconv.Atoi(scanner.Text())
		return res
	}

	if !scanner.Scan() {
		return
	}
	n, _ := strconv.Atoi(scanner.Text())

	f := make([]int, n+1)
	inDegree := make([]int, n+1)
	for i := 1; i <= n; i++ {
		f[i] = scanInt()
		inDegree[f[i]]++
	}

	compID := make([]int, n+1)
	var cycles []int
	var leavesOfComp [][]int

	currentComp := 0

	for i := 1; i <= n; i++ {
		if inDegree[i] == 0 {
			curr := i
			var path []int
			for compID[curr] == 0 {
				compID[curr] = -1
				path = append(path, curr)
				curr = f[curr]
			}

			c := compID[curr]
			if c == -1 {
				currentComp++
				c = currentComp
				cycles = append(cycles, curr)
				leavesOfComp = append(leavesOfComp, []int{})
			}
			for _, v := range path {
				compID[v] = c
			}
			leavesOfComp[c-1] = append(leavesOfComp[c-1], i)
		}
	}

	for i := 1; i <= n; i++ {
		if compID[i] == 0 {
			curr := i
			var path []int
			for compID[curr] == 0 {
				compID[curr] = -1
				path = append(path, curr)
				curr = f[curr]
			}

			c := compID[curr]
			if c == -1 {
				currentComp++
				c = currentComp
				cycles = append(cycles, curr)
				leavesOfComp = append(leavesOfComp, []int{curr})
			}
			for _, v := range path {
				compID[v] = c
			}
		}
	}

	numLeaves := 0
	for i := 1; i <= n; i++ {
		if inDegree[i] == 0 {
			numLeaves++
		}
	}

	if currentComp == 1 && numLeaves == 0 {
		fmt.Println(0)
		return
	}

	var ans [][]int
	k := currentComp
	for i := 0; i < k; i++ {
		u := cycles[i]
		v := leavesOfComp[(i+1)%k][0]
		ans = append(ans, []int{u, v})
		for j := 1; j < len(leavesOfComp[i]); j++ {
			ans = append(ans, []int{u, leavesOfComp[i][j]})
		}
	}

	fmt.Println(len(ans))
	writer := bufio.NewWriter(os.Stdout)
	for _, edge := range ans {
		fmt.Fprintf(writer, "%d %d\n", edge[0], edge[1])
	}
	writer.Flush()
}