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.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];
        int[] b = new int[n];
        int min = Integer.MAX_VALUE;
        int minPoint = 0;
        int max = Integer.MIN_VALUE;
        int maxPoint = 0;
        for (int i = 0; i < n; i++) {
            a[i] = sc.nextInt();
            if (min > a[i]) {
                min = a[i];
                minPoint = i;
            }
            if (max < a[i]) {
                max = a[i];
                maxPoint = i;
            }
            min = Math.min(min, a[i]);
            max = Math.max(max, a[i]);
        }
        int changeNum = 0;
        int pos = 0;
        if (Math.abs(min) > Math.abs(max)) {
            changeNum = min;
            pos = minPoint;
        } else {
            changeNum = max;
            pos = maxPoint;
        }
        // n - 1回の処理
        for (int i = 0; i < n; i++) {
            if (i != pos) {
                a[i] += changeNum;
            }
        }
        // 正の数の処理
        if (changeNum > 0) {
            for (int i = 0; i < n - 1; i++) {
                a[i + 1] = a[i];
            }
        } else {
            for (int i = 0; i < n - 1; i++) {
                a[n - 2 - i] += a[n - 1 - i];
            }
        }
        System.out.println(2 * n - 2);
        // n - 1回の処理
        for (int i = 0; i < n; i++) {
            if (pos == i)
                continue;
            System.out.println((pos + 1) + " " + (i + 1));
        }
        if (changeNum > 0) {
            for (int i = 1; i < n; i++) {
                System.out.println(i + " " + (i + 1));
            }
        } else {
            for (int i = n; i > 1; i--) {
                System.out.println(i + " " + (i - 1));
            }
        }
    }
}