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 max = -1000001;
        int min = 1000001;
        int maxi = 0;
        int mini = 0;

        for(int i=0; i<N; i++){
            A[i] = sc.nextInt();
            max = Math.max(max, A[i]);
            min = Math.min(min, A[i]);
            if(max==A[i]){
                maxi = i + 1;
            }
            if(min==A[i]){
                mini = i + 1;
            }
        }
        
        if(min>=0){
            System.out.println(N - 1);
            for(int i=1; i<=N-1; i++){
                System.out.println(i + " " + (int)(i + 1));
            }
        }
        else{
            System.out.println(2 * N - 1);
            if(Math.abs(max)>=Math.abs(min)){
                for(int i=1; i<=N; i++){
                    System.out.println(maxi + " " + i);
                }
                for(int i=1; i<=N-1; i++){
                    System.out.println(i + " " + (int)(i + 1));
                }
            }
            else{
                for(int i=1; i<=N; i++){
                    System.out.println(mini + " " + i);
                }
                for(int i=N - 1; i>=1; i--){
                    System.out.println(i + 1 + " " + i);
                }
            }
        }
    }
}