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.Scanner;

public class Main {

	public static void main(String[] args) 
	{
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		long[] a = new long[n];
		
		long min = 999999999;
		long max = -999999999;
		int miner = -1;
		int maxer = -1;
		for(int i = 0; i < n; i++)
		{
			a[i] = sc.nextLong();
			
			if(a[i]<min)
			{
				miner=i;
				min=a[i];
			}
			if(a[i]>max)
			{
				maxer=i;
				max=a[i];
			}
		}
		
		int ops = 0;
		StringBuilder sb = new StringBuilder();
		boolean allpos = false;
		if(max >= 0 && min >= 0)allpos = true;
		//mixed case
		if(min < 0 && max > 0 && max >= -min)
		{ //absolute largest is positive
			for(int i = 0; i < n; i++)
			{
				int id = i+1;
				if(i!=maxer)
				{
					sb.append((maxer+1) + " " + id + "\n");
					ops++;
				}
			}
			allpos = true;
		}
		else if(min < 0 && max > 0 && -min > max)
		{ //absolute largest is neg
			for(int i = 0; i < n; i++)
			{
				int id = i+1;
				if(i!=miner)
				{
					sb.append((miner+1) + " " + id + "\n");
					ops++;
				}
			}
			allpos = false;
		}
		
		if(allpos)
		{
			for(int i = 0; i < n-1; i++)
			{
				sb.append((i+1) + " " + (i+2) + "\n");
				ops++;
			}
		}
		else {
			for(int i = n-1; i>=1; i--)
			{
				sb.append((i+1) + " " + (i) + "\n");
				ops++;
			}
		}
		System.out.println(ops);
		System.out.print(sb);
		
	}

}