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: Wrong Answer)

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using static System.Console;
namespace AtCoder.ARC086
{
    class NonDecreasing
    {
        public static void Main()
        {
            var n = int.Parse(ReadLine());
            var nums = ReadLine().Trim().Split(' ').Select(_ => int.Parse(_)).ToArray();
            var min = nums.Min();
            var max = nums.Max();
            var minIndex = 0;
            var maxIndex = 0;
            for (var i = 0; i < nums.Count(); ++i)
            {
                if (nums[i] == min) minIndex = i + 1;
                if (nums[i] == max) maxIndex = i + 1;
            }
            if (min + max >= 0)
            {
                for (var i = 1; i <= n; ++i)
                {
                    WriteLine($"{maxIndex} {i}");
                }
                for (var i = 1; i < n; ++i)
                {
                    WriteLine($"{i} {i + 1}");
                }
            }
            else
            {
                for (var i = 1; i <= n; ++i)
                {
                    WriteLine($"{minIndex} {i}");
                }
                for (var i = n; i > 1; --i)
                {
                    WriteLine($"{i} {i - 1}");
                }
            }
        }
    }
}