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"
	"math"
	"os"
	"sort"
	"strconv"
	"strings"
)

var (
	sc = bufio.NewScanner(os.Stdin)
)

func main() {
	sc.Scan()
	n, _ := strconv.Atoi(sc.Text())
	sc.Scan()
	a := make([]int, n)
	for i, ai := range strings.Split(sc.Text(), " ") {
		a[i], _ = strconv.Atoi(ai)
	}

	steps := make([]string, 0, 2*n)

	first, last := 0, len(a)-1
	for last != first {
		sub := append([]int{}, a[first:last+1]...)
		sort.Sort(sort.Reverse(sort.IntSlice(sub)))

		if sub[1] > 0 || sub[0] > 0 && a[last] < sub[0] {
			max := math.MinInt64
			maxIdx := 0
			for i := first; i < last; i++ {
				if max < a[i] {
					max = a[i]
					maxIdx = i
				}
			}
			for max > a[last] {
				a[last] += max
				steps = append(steps, fmt.Sprintf("%d %d", maxIdx+1, last+1))
			}
			last--
		} else {
			min := math.MaxInt64
			minIdx := 0
			for i := first + 1; i <= last; i++ {
				if min > a[i] {
					min = a[i]
					minIdx = i
				}
			}
			for min < a[first] {
				a[first] += min
				steps = append(steps, fmt.Sprintf("%d %d", minIdx+1, first+1))
			}
			first++
		}
	}

	fmt.Println(len(steps))
	fmt.Println(strings.Join(steps, "\n"))
}