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 (1.6) (judge verdict: Wrong Answer)

package main

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

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

func solve(in io.Reader, out io.Writer) {
	var bs = NewBufScanner(in)
	var bw = NewBufWriter(out)
	defer bw.w.Flush()

	n := bs.IntScan()
	as := []int{}

	for i := 0; i < n; i++ {
		as = append(as,  bs.IntScan())
	}

	answers := []answer{}
	start := 0
	end := len(as)
	for {
		max := maxIndex(as[start:end])
		min := minIndex(as[start:end])

		if abs(as[max]) >= abs(as[min]) {
			for i := max + 1; i < n; i++ {
				for {
					if as[max] <= as[i] && as[i - 1] <= as[i] {
						break
					}
					as[i] += as[max]
					answers = append(answers, answer{x: max+1, y: i+1})
				}
			}
			end = max
		} else {
			for i := min - 1; i >= 0; i-- {
				for {
					if as[min] >= as[i] && as[i + 1] >= as[i] {
						break
					}
					as[i] += as[min]
					answers = append(answers, answer{x: min+1, y: i+1})
				}
			}
			start = min + 1
		}
		if start - end <= 1 {
			break
		}
	}

	bw.Printf("%d\n", len(answers))
	for _, a := range answers {
		bw.Printf("%d %d\n", a.x, a.y)
	}
}


type answer struct {
	x int
	y int
}

func maxIndex(l []int) int {
	max := math.MinInt32
	idx := -1
	for i, v := range l {
		if max < v {
			max = v
			idx = i
		}
	}
	return idx
}

func minIndex(l []int) int {
	min := math.MaxInt32
	idx := -1
	for i, v := range l {
		if min > v {
			min = v
			idx = i
		}
	}
	return idx
}


func abs(x int) int {
	return int(math.Abs(float64(x)))
}

// BufScanner original scanner
type BufScanner struct {
	s *bufio.Scanner
}

// NewBufScanner constructer
func NewBufScanner(in io.Reader) *BufScanner {
	s := bufio.NewScanner(in)
	s.Buffer(make([]byte, 1024), 1e+9)
	s.Split(bufio.ScanWords)
	return &BufScanner{
		s: s,
	}
}

// Scan Scan Data
func (b *BufScanner) Scan() string {
	b.s.Scan()
	return b.s.Text()
}

// IntScan Scan Data
func (b *BufScanner) IntScan() int {
	v, err := strconv.Atoi(b.Scan())
	if err != nil {
		panic(err)
	}
	return v
}

// BufWriter original writer
type BufWriter struct {
	w *bufio.Writer
}

// NewBufWriter constructer
func NewBufWriter(out io.Writer) *BufWriter {
	w := bufio.NewWriter(out)
	return &BufWriter{
		w: w,
	}
}

// Printf Output file
func (b *BufWriter) Printf(format string, a ...interface{}) {
	fmt.Fprintf(b.w, format, a...)
}