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 Java7 (OpenJDK 1.7.0) (judge verdict: Accepted)

import java.util.*;
import java.io.*;

public class Main {
	public static void main(String[] args) {
		Scanner in = new Scanner(System.in);
		int n = in.nextInt();
		int[] arr = new int[n];

		boolean allnegs = true;
		boolean allposs = true;

		int min = 0;
		int max = 0;
		for(int i = 0; i < n; ++i) {
			arr[i] = in.nextInt();

			if(arr[i] < 0)
				allposs = false;
			else if(arr[i] >= 0)
				allnegs = false;

			if(arr[min] > arr[i])
				min = i;
			if(arr[max] < arr[i])
				max = i;
		}



		ArrayList<Pair> li = new ArrayList();
		if(allnegs) {
			for(int i = n - 1; i > 0; --i) {
				li.add(new Pair(i , i - 1));
			}
		} else if(allposs) {
			for(int i = 1; i < n; ++i) {
				li.add(new Pair(i -1, i));
			}
		} else {
			if(Math.abs(arr[min]) <= arr[max]) {
				for(int i = 0; i < n; ++i) 
					if(i != max)
						li.add(new Pair(max, i));
				for(int i = 1; i < n; ++i) {
					li.add(new Pair(i - 1 , i));
				}
			} else {
				for(int i = 0; i < n; ++i) 
					if(i != min)
						li.add(new Pair(min, i));

				for(int i = n - 1; i > 0; --i) {
					li.add(new Pair(i , i - 1));
				}
			}
		}

		System.out.println(li.size());
		for(Pair p : li) {
			System.out.println(p);
		}
	}

	private static class Pair {
		int f, s;

		public Pair(int f, int s) {
			this.f = f;
			this.s = s;
		}

		@Override
		public String toString() {
			return (f+1)+" "+(s+1);
		}
	}

}