Problem:
Score : 600 points

Problem Statement

Snuke has an integer sequence, a, of length N. The i-th element of a (1-indexed) is a_{i}.

He can perform the following operation any number of times:

Operation: Choose integers x and y between 1 and N (inclusive), and add a_x to a_y.

He would like to perform this operation between 0 and 2N times (inclusive) so that a satisfies the condition below. Show one such sequence of operations.
It can be proved that such a sequence of operations always exists under the constraints in this problem.

Condition: a_1 \leq a_2 \leq ... \leq a_{N}

Constraints

2 \leq N \leq 50

-10^{6} \leq a_i \leq 10^{6}

All input values are integers.

Input

Input is given from Standard Input in the following format:

N
a_1 a_2 ... a_{N}

Output

Let m be the number of operations in your solution. In the first line, print m.
In the i-th of the subsequent m lines, print the numbers x and y chosen in the i-th operation, with a space in between.
The output will be considered correct if m is between 0 and 2N (inclusive) and a satisfies the condition after the m operations.

Sample Input 1

3
-2 5 -1

Sample Output 1

2
2 3
3 3

After the first operation, a = (-2,5,4).

After the second operation, a = (-2,5,8), and the condition is now satisfied.

Sample Input 2

2
-1 -3

Sample Output 2

1
2 1

After the first operation, a = (-4,-3) and the condition is now satisfied.

Sample Input 3

5
0 0 0 0 0

Sample Output 3

0

The condition is satisfied already in the beginning.

Solution in Go (1.14.1) (judge verdict: Accepted)

package main

import (
	"bufio"
	. "fmt"
	"io"
	"os"
)

// github.com/EndlessCheng/codeforces-go
func run(_r io.Reader, _w io.Writer) {
	in := bufio.NewReader(_r)
	out := bufio.NewWriter(_w)
	defer out.Flush()

	var n, minI, maxI int
	Fscan(in, &n)
	a := make([]int, n)
	for i := range a {
		Fscan(in, &a[i])
		if a[i] < a[minI] {
			minI = i
		} else if a[i] > a[maxI] {
			maxI = i
		}
	}
	ans := [][]int{}
	d := 1
	if a[minI] < 0 && a[maxI] > 0 {
		if a[maxI] > -a[minI] {
			for i, v := range a {
				if v < 0 {
					ans = append(ans, []int{maxI + 1, i + 1})
				}
			}
		} else {
			for i, v := range a {
				if v > 0 {
					ans = append(ans, []int{minI + 1, i + 1})
				}
			}
			d = 0
		}
	} else if a[maxI] <= 0 {
		d = 0
	}
	if d == 1 {
		for i := 1; i < n; i++ {
			ans = append(ans, []int{i, i + 1})
		}
	} else {
		for i := n; i > 1; i-- {
			ans = append(ans, []int{i, i - 1})
		}
	}
	Fprintln(out, len(ans))
	for _, p := range ans {
		Fprintln(out, p[0], p[1])
	}
}

func main() { run(os.Stdin, os.Stdout) }