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;

public static class P
{
    public static void Main()
    {
        int n = int.Parse(Console.ReadLine());
        var a = Console.ReadLine().Split().Select(int.Parse).ToArray();
        var min = a.Min();
        var max = a.Max();
        Console.WriteLine(2 * n);
        if (min + max < 0)
        {
            var minInd = Array.IndexOf(a, min) + 1;
            Console.WriteLine($"{minInd} {minInd}");
            for (int i = 1; i <= n; i++) Console.WriteLine($"{minInd} {i}");
            for (int i = n; i >= 2; i--) Console.WriteLine($"{i} {i - 1}");
        }
        else
        {
            var maxInd = Array.IndexOf(a, max) + 1;
            Console.WriteLine($"{maxInd} {maxInd}");
            for (int i = 1; i <= n; i++) Console.WriteLine($"{maxInd} {i}");
            for (int i = 1; i <= n - 1; i++) Console.WriteLine($"{i} {i + 1}");
        }
    }
}