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.Linq;

namespace test
{
    class Program
    {
        static void Main(string[] args)
        {
            var N = ReadInt();
            var a = ReadArrayInt();
            var max = a[0];
            var maxidx = 0;
            var min = a[0];
            var minidx = 0;
            for (int i = 1; i < N; i++)
            {
                if (a[i] > max)
                {
                    max = a[i];
                    maxidx = i;
                }
                else if (a[i] < min)
                {
                    min = a[i];
                    minidx = i;
                }
            }

            var cnt = 0;
            var ope = new List<int[]>();

            if (max >= 0 && min >= 0)
            {
                for (int i = 0; i < N - 1; i++)
                {
                    ope.Add(new int[] { i + 1, i + 2 });
                    cnt++;
                }
            }
            else if (max <= 0 && min <= 0)
            {
                for (int i = N; i > 1; i--)
                {
                    ope.Add(new int[] { i, i - 1 });
                    cnt++;
                }
            }
            else
            {
                if (Math.Abs(max) >= Math.Abs(min))
                {
                    for (int i = 0; i < N; i++)
                    {
                        ope.Add(new int[] { maxidx + 1, i + 1 });
                        cnt++;
                    }
                    for (int i = 0; i < N - 1; i++)
                    {
                        ope.Add(new int[] { i + 1, i + 2 });
                        cnt++;
                    }
                }
                else
                {
                    for (int i = 0; i < N; i++)
                    {
                        ope.Add(new int[] { minidx + 1, i + 1 });
                        cnt++;
                    }
                    for (int i = N; i > 1; i--)
                    {
                        ope.Add(new int[] { i, i - 1 });
                        cnt++;
                    }
                }                
            }

            Console.WriteLine(cnt);
            foreach (var o in ope) Console.WriteLine(o[0] + " " + o[1]);

            Console.WriteLine();
            Console.ReadLine();
        }

        static string Read() { return Console.ReadLine(); }
        static int ReadInt() { return int.Parse(Read()); }
        static long ReadLong() { return long.Parse(Read()); }
        static int[] ReadArrayInt() { return Read().Split(' ').Select(s => int.Parse(s)).ToArray(); }
        static long[] ReadArrayLong() { return Read().Split(' ').Select(s => long.Parse(s)).ToArray(); }
    }
}