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 C# (Mono 4.6.2.0) (judge verdict: Wrong Answer)

using System;
using System.IO;
using System.Linq;
using System.Numerics;
using System.Collections;
using System.Collections.Generic;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;
using static System.Math;
using LayoutKind = System.Runtime.InteropServices.LayoutKind;
using StructLayoutAttribute = System.Runtime.InteropServices.StructLayoutAttribute;
using FieldOffsetAttribute = System.Runtime.InteropServices.FieldOffsetAttribute;
using MethodImplOptions = System.Runtime.CompilerServices.MethodImplOptions;
using MethodImplAttribute = System.Runtime.CompilerServices.MethodImplAttribute;

static class P
{
    static void Main()
    {
        //絶対値のmaxの奴を2回足すと
        int n = int.Parse(Console.ReadLine());
        var a = Console.ReadLine().Split().Select(int.Parse).ToArray();

        int max = -1;
        int maxInd = -1;
        for (int i = 0; i < a.Length; i++)
        {
            if (max < Abs(a[i]))
            {
                max = Abs(a[i]);
                maxInd = i;
            }
        }

        List<Tuple<int, int>> ops = new List<Tuple<int, int>>();
        int currentInd = a[maxInd] > 0 ? 0 : n - 1;
        int next = a[maxInd] > 0 ? 1 : -1;
        ops.Add(new Tuple<int, int>(maxInd, currentInd));
        ops.Add(new Tuple<int, int>(maxInd, currentInd));
        currentInd += next;
        while (0 <= currentInd && currentInd < n)
        {
            ops.Add(new Tuple<int, int>(currentInd, currentInd - next));
            ops.Add(new Tuple<int, int>(currentInd, currentInd - next));
            currentInd += next;
        }
        Console.WriteLine(ops.Count);
        Console.WriteLine(string.Join("\n", ops.Select(x => $"{x.Item1} {x.Item2}")));
    }
}