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.*;

class Main
{
    public static void main (String[] args)
    {
        Scanner sc = new Scanner(System.in);
        int n = sc.nextInt();
        int[] a = new int[n];
        int[] x = new int[2 * n];
        int[] y = new int[2 * n];
        int max = 0;
        int max_index = 0;
        int min = 0;
        int min_index = 0;
        for(int i = 0; i < n; i++){
            a[i] = sc.nextInt();
            if(max < a[i]){
                max = a[i];
                max_index = i;
            }
            if(min > a[i]){
                min = a[i];
                min_index = i;
            }
        }
        if(Math.abs(min) < max){
            for(int i = 0; i < n; i++){
                y[i] = i + 1;
                x[i] = max_index + 1;
            }
            for(int i = n; i < 2 * n - 1; i++){
                x[i] = i - n + 1;
                y[i] = i - n + 2;
            }
        }
        else{
            for(int i = 0; i < n; i++){
                y[i] = i + 1;
                x[i] = min_index + 1;
            }
            for(int i = n; i < 2 * n - 1; i++){
                x[i] =  2 * n  - i ;
                y[i] = 2 * n - 1 - i;
            }    
        }
        System.out.println(2 * n - 1);
        for(int i = 0; i < 2 * n - 1; i++){
            System.out.println(x[i] + " " + y[i]);
        }
    }
}