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.Linq;

class D
{
	static void Main()
	{
		var n = int.Parse(Console.ReadLine());
		var a = Console.ReadLine().Split().Select(long.Parse).ToArray();

		var M = a.Max(v => Math.Abs(v));
		var x = Enumerable.Range(0, n).First(i => Math.Abs(a[i]) == M);

		var r = new string[0].ToList();
		if (a[x] >= 0)
		{
			for (int i = 1; i < n; i++)
			{
				while (a[i - 1] > a[i])
				{
					a[i] += a[x];
					r.Add($"{x + 1} {i + 1}");
				}
				if (a[i] > a[x]) x = i;
			}
		}
		else
		{
			for (int i = n - 2; i >= 0; i--)
			{
				while (a[i] > a[i + 1])
				{
					a[i] += a[x];
					r.Add($"{x + 1} {i + 1}");
				}
				if (a[i] < a[x]) x = i;
			}
		}

		Console.WriteLine(r.Count);
		Console.WriteLine(string.Join("\n", r));
	}
}