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.Arrays;
import java.util.Scanner;

public class Main {
	void run() {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] a = new int[n];
		int max = -1000001;
		int max_num = 0;
		int min = 1000001;
		int min_num = 0;
		for(int i = 0; i < n; i++) {
			a[i] = sc.nextInt();
			if(a[i] > max) {
				max = a[i];
				max_num = i;
			}
			if(a[i] < min) {
				min = a[i];
				min_num = i;
			}
		}
		int max_abs = Math.max(Math.abs(max), Math.abs(min));
		System.out.println((n-1)*2);
		int aa = 0;
		if(max_abs == Math.abs(max))aa=max;
		else if(max_abs == Math.abs(min))aa = min;
		
		if(max_abs == Math.abs(max)) {
			for(int i = 0; i < n; i++) {
				if(max_num == i)continue;
				System.out.println((max_num+1) + " " + (i+1));
			}	
		}else if(max_abs == Math.abs(min)) {
			for(int i = 0; i < n; i++) {
				if(min_num == i)continue;
				System.out.println((min_num+1) + " " + (i+1));
			}	
		}
		
		if(aa >= 0) {
			for(int i = 0; i < n-1; i++) {
				System.out.println((i+1) + " " + (i+2));
			}
		}else {
			for(int i = n-1; i > 0; i--) {
				System.out.println((i+1) + " " + i);
			}
		}
			
		sc.close();
	}

	void debug(Object... o) {
		System.out.println(Arrays.deepToString(o));
	}

	public static void main(String[] args) {
		new Main().run();
	}
}