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];
		int pos = 0, neg = 0, max = 0;
		for(int i=0;i<n;i++) {
			a[i] = sc.nextInt();
			if(a[i]>0)
				pos++;
			if(a[i]<0)
				neg++;
			if(Math.abs(a[i])>Math.abs(a[max]))
				max = i;
		}
		
		if(pos==0 && neg==0) {
			System.out.println(0);
		}
		else {
			int m = 0;
			StringBuilder ans = new StringBuilder();
			
			if(pos!=0 && neg!=0) {
				if(a[max]>0) {
					for(int i=0;i<n;i++) {
						if(a[i]<0) {
							a[i]+=a[max];
							m++;
							ans.append((max+1)+" "+(i+1)+"\n");
						}
					}
					neg = 0;
				}
				else {
					for(int i=0;i<n;i++) {
						if(a[i]>0) {
							a[i]+=a[max];
							m++;
							ans.append((max+1)+" "+(i+1)+"\n");
						}
					}
					pos = 0;
				}
			}
			
			if(pos==0) {
				for(int i=n-1;i>=1;i--) {
					if(a[i-1]>a[i]) {
						a[i-1]+=a[i];
						m++;
						ans.append((i+1)+" "+(i)+"\n");
					}
				}
			}
			else {
				for(int i=0;i<n-1;i++) {
					if(a[i]>a[i+1]) {
						a[i+1]+=a[i];
						m++;
						ans.append((i+1)+" "+(i+2)+"\n");
					}
				}
			}
			
			System.out.println(m);
			System.out.print(ans);
		}
	}
}