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 Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.util.*;

public class Main {
	public static void main (String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int max = Integer.MIN_VALUE;
		int maxIdx = 0;
		int min = Integer.MAX_VALUE;
		int minIdx = 0;
		for (int i = 0; i < n; i++) {
		    int x = sc.nextInt();
		    if (max < x) {
		        max = x;
		        maxIdx = i + 1;
		    }
		    if (min > x) {
		        min = x;
		        minIdx = i + 1;
		    }
		}
		StringBuilder sb = new StringBuilder();
		if (Math.abs(max) >= Math.abs(min)) {
		    for (int i = 1; i <= n; i++) {
		        sb.append(maxIdx).append(" ").append(i).append("\n");
		    }
		    for (int i = 1; i < n; i++) {
		        sb.append(i).append(" ").append(i + 1).append("\n");
		    }
		} else {
		    for (int i = 1; i <= n; i++) {
		        sb.append(minIdx).append(" ").append(i).append("\n");
		    }
		    for (int i = n; i > 1; i--) {
		        sb.append(i).append(" ").append(i - 1).append("\n");
		    }
		}
		System.out.println(n * 2 - 1);
		System.out.print(sb);
    }
}