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.Text;
//1001 Exponentiation
namespace OJ_C_Sharp {
    class Program {
        
        static void Main(string[] args) {
            int N = int.Parse(Console.ReadLine());
            var input = Console.ReadLine().Split(' ');
            int[] a = new int[N];
            for (int i = 0; i < N;i++){
                a[i] = int.Parse(input[i]);
            }
            int min = a[0];
            int max = a[0];
            int min_index = 1;
            int max_index = 1;
            for (int i = 1; i < N;i++){
                if (min>a[i]){
                    min = a[i];
                    min_index = i + 1;
                }
                if(max<a[i]){
                    max = a[i];
                    max_index = i + 1;
                }
            }
            int m = 2 * N - 1;
            if (System.Math.Abs(min)>System.Math.Abs(max)){
                Console.WriteLine(m);
                for (int i = 1; i <= N;i++){
                    Console.WriteLine("{0} {1}",min_index,i);
                }
                for (int i = N; i > 1;i--){
                    Console.WriteLine("{0} {1}",i,i-1);
                }
            }
            else {
                Console.WriteLine(m);
                for (int i = 1; i <= N ;i++){
                    Console.WriteLine("{0} {1}",max_index,i);
                }
                for (int i = 1; i < N;i++){
                    Console.WriteLine("{0} {1}",i,i+1);
                }
            }
        }
    }
}