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: Time Limit Exceeded)

//#pragma warning disable
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System;
using System.Numerics;
using System.Threading.Tasks;
using static System.Math;
using static System.Console;
class Z { static void Main() => new K(); }
class K
{
	int F() => int.Parse(ReadLine());
	long FL() => long.Parse(ReadLine());
	int[] G() => ReadLine().Split(new char[] { ' ', '\t' }, StringSplitOptions.RemoveEmptyEntries).Select(int.Parse).ToArray();
	long[] GL() => ReadLine().Split(new char[] { ' ', '\t' }, StringSplitOptions.RemoveEmptyEntries).Select(long.Parse).ToArray();
	public const int MOD = 1000000007;
	public K()
	{
		SetOut(new StreamWriter(OpenStandardOutput()) { AutoFlush = false });
		Solve();
		Out.Flush();
	}
	void Solve()
	{
		var N = F();
		var A = G();
		int m = A.Min(), M = A.Max(), mi = 0, Mi = 0;
		while (A[mi] != m) mi++;
		while (A[Mi] != M) Mi++;
		if (m >= 0)
		{
			Console.WriteLine(N - 1);
			for (var i = 1; i < N; i++) Console.WriteLine("{0} {1}", i, i + 1);
		}
		else if (M <= 0)
		{
			Console.WriteLine(N - 1);
			for (var i = N - 1; i > 0; i++) Console.WriteLine("{0} {1}", i + 1, i);
		}
		// m < 0 && M > 0
		else if (M >= -m)
		{
			Console.WriteLine(2 * N - 1);
			for (var i = 0; i < N; i++) Console.WriteLine("{0} {1}", Mi + 1, i + 1);
			for (var i = 1; i < N; i++) Console.WriteLine("{0} {1}", i, i + 1);
		}
		else
		{
			Console.WriteLine(2 * N - 1);
			for (var i = 0; i < N; i++) Console.WriteLine("{0} {1}", mi + 1, i + 1);
			for (var i = N - 1; i > 0; i++) Console.WriteLine("{0} {1}", i + 1, i);
		}
	}
}