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.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        int N = Integer.parseInt(sc.next());
        long[] A = new long[N];
        long plus_max=0;
        int plus_max_index=-1;
        long minus_min=0;
        int minus_min_index=-1;
        for (int i=0;i<N;i++) {
            A[i] = Long.parseLong(sc.next());
            if (A[i]>0) {
                if (A[i]>plus_max) {
                    plus_max = A[i];
                    plus_max_index = i;
                }
            } else if (A[i]<0) {
                if (A[i]<minus_min) {
                    minus_min = A[i];
                    minus_min_index = i;
                }
            }
        }
        if (plus_max_index==-1 && minus_min_index==-1) {
            System.out.println(0);
        } else if (plus_max+minus_min>0) {
            System.out.println((2*N-1));
            for (int i=0;i<N;i++) {
                System.out.println((plus_max_index+1) + " " + (i+1));
            }
            for (int i=0;i<N-1;i++) {
                System.out.println((i+1) + " " + (i+2));
            }
        } else {
            System.out.println((2*N-1));
            for (int i=0;i<N;i++) {
                System.out.println((minus_min_index+1) + " " + (i+1));
            }
            for (int i=N-1;i>0;i--) {
                System.out.println((i+1) + " " + (i));
            }
        }
    }
}