Problem: 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.

Examples

Input

3
-2 5 -1


Output

2
2 3
3 3


Input

2
-1 -3


Output

1
2 1


Input

5
0 0 0 0 0


Output

0

Solution (in JAVA):

Solution:
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int n = Integer.parseInt(sc.next());
        int[] a = new int[n];
        int min = Integer.MAX_VALUE;
        int minIndex = 0;
        int max = Integer.MIN_VALUE;
        int maxIndex = 0;
        for (int i = 0; i < n; i++) {
            a[i] = Integer.parseInt(sc.next());
            min = Math.min(min, a[i]);
            if (min == a[i]) {
                minIndex = i;
            }
            max = Math.max(max, a[i]);
            if (max == a[i]) {
                maxIndex = i;
            }
        }
        System.out.println(2 * n - 2);
        if (Math.abs(max) >= Math.abs(min) || min >= 0) {
            for (int i = 0; i < n; i++) {
                if (i != maxIndex) {
                    System.out.println((maxIndex + 1) + " " + (i + 1));
                }
            }
            for (int i = 0; i < n - 1; i++) {
                System.out.println((i + 1) + " " + (i + 2));
            }
        } else {
            for (int i = 0; i < n; i++) {
                if (i != minIndex) {
                    System.out.println((minIndex + 1) + " " + (i + 1));
                }
            }
            for (int i = 0; i < n - 1; i++) {
                System.out.println((n - i) + " " + (n - i - 1));
            }
        }
    }
}