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: Accepted)

using System;
using System.Collections.Generic;
using System.Text;

namespace AtTest.D_Challenge
{
    class ABC_081
    {
        static void Main(string[] args)
        {
            Method(args);
            Console.ReadLine();
        }

        static void Method(string[] args)
        {
            int n = ReadInt();
            long[] array = ReadLongs();
            int absMaxIndex = 0;
            for(int i = 1; i < n; i++)
            {
                if (Math.Abs(array[absMaxIndex]) < Math.Abs(array[i]))
                {
                    absMaxIndex = i;
                }
            }
            var handles = new List<int[]>();
            for(int i = 0; i < n; i++)
            {
                if (array[i] * array[absMaxIndex] < 0)
                {
                    handles.Add(new int[2] { absMaxIndex + 1, i + 1 });
                    array[i] += array[absMaxIndex];
                }
            }
            if (array[absMaxIndex] > 0)
            {
                for (int i = 1; i < n; i++)
                {
                    if (array[i] - array[i - 1] < 0)
                    {
                        handles.Add(new int[2] { i, i + 1 });
                        array[i] += array[i - 1];
                    }
                }
            }
            else if (array[absMaxIndex] < 0)
            {
                for (int i = n - 2; i >= 0; i--)
                {
                    if (array[i + 1] - array[i] < 0)
                    {
                        handles.Add(new int[2] { i + 2, i + 1 });
                        array[i] += array[i + 1];
                    }
                }
            }

            Console.WriteLine(handles.Count);
            for(int i = 0; i < handles.Count; i++)
            {
                Console.WriteLine(handles[i][0] + " " + handles[i][1]);
            }
            /*for(int i = 0; i < n; i++)
            {
                Console.Write(array[i] + " ");
            }*/
        }

        private static string Read() { return Console.ReadLine(); }
        private static int ReadInt() { return int.Parse(Read()); }
        private static long ReadLong() { return long.Parse(Read()); }
        private static double ReadDouble() { return double.Parse(Read()); }
        private static int[] ReadInts() { return Array.ConvertAll(Read().Split(), int.Parse); }
        private static long[] ReadLongs() { return Array.ConvertAll(Read().Split(), long.Parse); }
        private static double[] ReadDoubles() { return Array.ConvertAll(Read().Split(), double.Parse); }
    }
}