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: Wrong Answer)

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] a = new int[n];
		for (int i = 0; i < n; i++) {
			a[i] = sc.nextInt();
		}
		sc.close();

		List<Answer> ans = new ArrayList<>();
		for (int i = 0; i < n - 1; i++) {
			if (a[i] <= a[i + 1]) {
				continue;
			} else if (a[i] > 0){
				ans.add(new Answer(i, true));
				a[i + 1] = a[i] + a[i + 1];
				i--;
			} else if (a[i] <= 0) {
				ans.add(new Answer(i + 1, false));
				a[i] = a[i] + a[i + 1];
				i--;
			}
		}
		System.out.println(ans.size());
		for (Answer answer : ans) {
			if (answer.isPositive()) {
				System.out.print(answer.getIndex() + 1);
				System.out.print(" ");
				System.out.println(answer.getIndex() + 2);
			} else {
				System.out.print(answer.getIndex() + 1);
				System.out.print(" ");
				System.out.println(answer.getIndex());
			}
		}
	}
}

class Answer {
	private int index;
	private boolean positive;
	public Answer(int index, boolean positive) {
		this.index = index;
		this.positive = positive;
	}
	public int getIndex() {
		return index;
	}
	public boolean isPositive() {
		return positive;
	}
}