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 = sc.nextInt();
		int[][] a = new int[N][2];
		for(int i = 0; i < N; i++) {
			a[i][0] = i;
			a[i][1] = sc.nextInt();
		}
		Arrays.sort(a, (x, y) -> x[1] - y[1]);
		System.out.println(2 * N - 1);
		if(Math.abs(a[0][1]) > a[N-1][1]) {
			for(int i = 0; i < N; i++)
				System.out.println((a[0][0]+1) + " " + (i + 1));
			for(int i = N-1; i > 0; i--)
				System.out.println((i+1) + " " + i);
		}
		else {
			for(int i = 0; i < N; i++)
				System.out.println((a[N-1][0]+1) + " " + (i + 1));
			for(int i = 1; i <= N-1; i++)
				System.out.println(i + " " + (i+1));
		}
	}

}