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 implements Runnable {

    public static void main(String[] args) {
        new Thread(null, new Main(), "", 128 * 1024 * 1024).start();
    }

    public void run() {
        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();
        }

        List<Pair> pairs = new ArrayList<>();
        int max = 0;
        for (int i = 0; i < N; i++) {
            if (Math.abs(a[i]) > Math.abs(a[max])) {
                max = i;
            }
        }
        if (a[max] > 0) {
            for (int i = max + 1; i < N; i++) {
                while (a[i - 1] > a[i]) {
                    a[i] += a[max];
                    pairs.add(new Pair(max + 1, i + 1));
                }
            }
            int min = 0;
            for (int i = 0; i < max; i++) {
                if (a[i] < a[min]) {
                    min = i;
                }
            }
            for (int i = max - 1; i > 0; i--) {
                while (a[i - 1] > a[i]) {
                    a[i - 1] += a[min];
                    pairs.add(new Pair(min + 1, i));
                }
            }
        } else {
            for (int i = max; i >= 1; i--) {
                while (a[i - 1] > a[i]) {
                    a[i - 1] += a[max];
                    pairs.add(new Pair(max + 1, i));
                }
            }
            int min = max + 1;
            for (int i = max + 1; i < N; i++) {
                if (a[i] > a[min]) {
                    min = i;
                }
            }
            for (int i = max + 1; i < N; i++) {
                while (a[i - 1] > a[i]) {
                    a[i] += a[min];
                    pairs.add(new Pair(min + 1, i + 1));
                }
            }
        }

        System.out.println(pairs.size());
        for (int i = 0; i < pairs.size(); i++) {
            System.out.println(pairs.get(i).x + " " + pairs.get(i).y);
        }
    }

    class Pair {

        public Pair(int x, int y) {
            this.x = x;
            this.y = y;
        }

        int x;
        int y;
    }
}