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 < a.length; ++i) {
            a[i] = sc.nextInt();
        }

        System.out.println(solve(a));

        sc.close();
    }

    static String solve(int[] a) {
        int minIndex = 0;
        int maxIndex = 0;
        for (int i = 1; i < a.length; ++i) {
            if (a[i] < a[minIndex]) {
                minIndex = i;
            }
            if (a[i] > a[maxIndex]) {
                maxIndex = i;
            }
        }

        List<String> operations = new ArrayList<>();
        if (a[minIndex] + a[maxIndex] >= 0) {
            for (int i = 0; i < a.length; ++i) {
                operations.add(String.format("%d %d", minIndex + 1, i + 1));
            }

            for (int i = 0; i < a.length - 1; ++i) {
                operations.add(String.format("%d %d", i + 1, i + 2));
            }
        } else {
            for (int i = 0; i < a.length; ++i) {
                operations.add(String.format("%d %d", maxIndex + 1, i + 1));
            }

            for (int i = a.length - 1; i >= 1; --i) {
                operations.add(String.format("%d %d", i + 1, i));
            }
        }

        return String.format("%d\n%s", operations.size(), String.join("\n", operations));
    }
}