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();
        long[] a = new long[N+1];
        long max = Long.MIN_VALUE;
        long min = Long.MAX_VALUE;
        int maxPos = -1;
        int minPos = -1;
        for(int i=1;i<=N;i++){
            a[i] = sc.nextLong();
            if(max<a[i]){
                max = a[i];
                maxPos = i;
            }
            if(min>a[i]){
                min = a[i];
                minPos = i;
            }
        }
        if(max==min){
            System.out.println(0);
            System.exit(0);
        }
        if(Math.abs(max)>=Math.abs(min)){
            System.out.println(2*N-1);
            for(int i=1;i<=N;i++){
                StringBuilder sb = new StringBuilder();
                sb.append(maxPos);
                sb.append(" ");
                sb.append(i);
                System.out.println(sb.toString());
            }
            for(int i=1;i<N;i++){
                StringBuilder sb = new StringBuilder();
                sb.append(i);
                sb.append(" ");
                sb.append(i+1);
                System.out.println(sb.toString());
            }
        }
        else{
            System.out.println(2*N-1);
            for(int i=1;i<=N;i++){
                StringBuilder sb = new StringBuilder();
                sb.append(minPos);
                sb.append(" ");
                sb.append(i);
                System.out.println(sb.toString());
            }
            for(int i=N;i>=2;i--){
                StringBuilder sb = new StringBuilder();
                sb.append(i);
                sb.append(" ");
                sb.append(i-1);
                System.out.println(sb.toString());
            }
        }
    }
}