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.IO;
using System.Linq;

namespace E
{
	internal class Program
	{
		static StreamWriter sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };

		public static void Main(string[] args)
		{
			var n = int.Parse(Console.ReadLine());
			var an = Console.ReadLine().Split().Select(int.Parse).ToList();
			var max = an.Max();
			var min = an.Min();
			var allPlusNum = max + min > 0 ? max : min;
			var isPlusMode = allPlusNum >= 0;
			var allPlusNumIdx = an.FindIndex(a => a == allPlusNum);

			an = an.ConvertAll(a => a += allPlusNum);
			an[allPlusNumIdx] -= allPlusNum;

			var secondList = new List<int>(n);
			if (isPlusMode)
			{
				for (var i = 0; i < n - 1; i++)
				{
					if (an[i] > an[i + 1])
					{
						an[i + 1] += an[i];
						secondList.Add(i + 1);
					}
				}
			}
			else
			{
				for (var i = n - 1; i >= 1; i--)
				{
					if (an[i - 1] > an[i])
					{
						an[i - 1] += an[i];
						secondList.Add(i + 1);
					}
				}
			}

			sw.WriteLine(n - 1 + secondList.Count);

			for (var i = 0; i < n; i++)
			{
				if (i != allPlusNumIdx) { sw.WriteLine($"{allPlusNumIdx + 1} {i + 1}"); }
			}

			foreach (var ax in secondList) { sw.WriteLine($"{ax} {ax + (isPlusMode ? 1 : -1)}"); }

			sw.Flush();
		}
	}
}