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.ArrayList;
import java.util.List;
import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int n = sc.nextInt();
		int[] a = new int[n];
		for (int i = 0; i < n; i++) {
			a[i] = sc.nextInt();
		}
		sc.close();

		int maxAbsIndex = 0;
		int tmpMax = 0;
		for (int i = 0; i < n; i++) {
			tmpMax = Math.max(Math.abs(a[i]), tmpMax);
			if (Math.abs(a[i]) >= tmpMax) {
				maxAbsIndex = i;
			}

		}

		List<Answer> ans = new ArrayList<>();
		if (a[maxAbsIndex] < 0) {
			for (int i = 0; i < n; i++) {
				if (i != maxAbsIndex) {
					a[i] = a[i] + a[maxAbsIndex];
					ans.add(new Answer(maxAbsIndex, i));
				}
			}
			for (int i = n - 1; i >= 1; i--) {
				if (a[i] < a[i - 1]) {
					a[i - 1] = a[i - 1] + a[i];
					ans.add(new Answer(i, i - 1));
					i++;
				}
			}
		} else if (a[maxAbsIndex] > 0) {
			for (int i = 0; i < n; i++) {
				if (i != maxAbsIndex) {
					a[i] = a[i] + a[maxAbsIndex];
					ans.add(new Answer(maxAbsIndex, i));
				}
			}
			for (int i = 0; i < n - 1; i++) {
				if (a[i] > a[i + 1]) {
					a[i + 1] = a[i] + a[i + 1];
					ans.add(new Answer(i, i + 1));
					i--;
				}
			}
		}
		System.out.println(ans.size());
		for (Answer answer : ans) {
			System.out.print(answer.getFrom() + 1);
			System.out.print(" ");
			System.out.println(answer.getTo() + 1);
		}
	}
}

class Answer {
	private int from;
	private int to;
	public Answer(int from, int to) {
		this.from = from;
		this.to = to;
	}
	public int getFrom() {
		return from;
	}
	public int getTo() {
		return to;
	}
}