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;

public class Hello
{
    public static void Main()
    {
        var n = int.Parse(Console.ReadLine().Trim());
        string[] line = Console.ReadLine().Trim().Split(' ');
        var a = Array.ConvertAll(line, int.Parse);
        var amax = -999999999;  var amaxi = -1;
        var amin = 999999999;  var amini = -1;
        for (int i = 0; i < n; i++)
        {
            if (a[i] > amax) { amax = a[i]; amaxi = i + 1; }
            if (a[i] < amin) { amin = a[i];  amini = i + 1; }
        }
        if (amax <= 0) putAllM(n);
        else if (amin >= 0) putAllP(n);
        else
        {
            if (amax >= -amin) { plusAll(amaxi, n); putAllP(n); }
            else { plusAll(amini, n); putAllM(n); }
        }
    }
    public  static void plusAll (int a, int n)
    {
        for (int i = 1; i <= n; i++)
            Console.WriteLine("{0} {1}", a, i);
    }
    public static void putAllP(int n)
    {
        for (int i = 1; i <= n - 1; i++)
            Console.WriteLine("{0} {1}", i, i + 1);
    }
    public static void putAllM (int n)
    {
        for (int i = n; i >= 2; i--)
            Console.WriteLine("{0} {1}", i, i - 1);
    }
}