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.awt.Point;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
import java.util.StringTokenizer;

public class Main {

	public static void main(String[] args) throws Exception {
		FastScanner scanner = new FastScanner(System.in);
		int size = (int) scanner.nextInt();
		int[] nums = scanner.nextIntArray(size);

		List<Point> list = new ArrayList<>();

		int max = Integer.MIN_VALUE;
		int min = Integer.MAX_VALUE;
		int maxIndex = -1;
		int minIndex = -1;

		for (int i = 0; i < nums.length; i++) {
			int num = nums[i];
			if (num > max) {
				max = num;
				maxIndex = i;
			}
			if (num < min) {
				min = num;
				minIndex = i;
			}
		}

		boolean isAllNeg = true;

		if (min >= 0) {
			isAllNeg = false;
		}
		if (max <= 0) {
			isAllNeg = true;
		} else {
			int value = min;
			int valueIndex = minIndex;
			if (Math.abs(min) <= Math.abs(max)) {
				value = max;
				valueIndex = maxIndex;
				isAllNeg = false;
			}
			for (int i = 0; i < nums.length; i++) {
				nums[i] += value;
				list.add(new Point(valueIndex, i));
			}
		}

		if (!isAllNeg) {
			for (int i = 1; i < nums.length; i++) {
				if (nums[i - 1] > nums[i]) {
					nums[i] += nums[i - 1];
					list.add(new Point(i - 1, i));
				}
			}
		} else {
			for (int i = nums.length - 2; i >= 0; i--) {
				if (nums[i] > nums[i + 1]) {
					nums[i] += nums[i + 1];
					list.add(new Point(i + 1, i));
				}
			}
		}

		System.out.println(list.size());
		list.forEach(p -> {
			System.out.println((p.x + 1) + " " + (p.y + 1));
		});
	}

	static class FastScanner {
		private BufferedReader reader = null;
		private StringTokenizer tokenizer = null;

		public FastScanner(InputStream in) {
			reader = new BufferedReader(new InputStreamReader(in));
			tokenizer = null;
		}

		public String next() {
			if (tokenizer == null || !tokenizer.hasMoreTokens()) {
				try {
					tokenizer = new StringTokenizer(reader.readLine());
				} catch (IOException e) {
					throw new RuntimeException(e);
				}
			}
			return tokenizer.nextToken();
		}

		public String nextLine() {
			if (tokenizer == null || !tokenizer.hasMoreTokens()) {
				try {
					return reader.readLine();
				} catch (IOException e) {
					throw new RuntimeException(e);
				}
			}

			return tokenizer.nextToken("\n");
		}

		public long nextLong() {
			return Long.parseLong(next());
		}

		public long nextInt() {
			return Integer.parseInt(next());
		}

		public double nextDouble() {
			return Double.parseDouble(next());
		}

		public int[] nextIntArray(int n) {
			int[] a = new int[n];
			for (int i = 0; i < n; i++)
				a[i] = (int) nextInt();
			return a;
		}

		public long[] nextLongArray(int n) {
			long[] a = new long[n];
			for (int i = 0; i < n; i++)
				a[i] = nextLong();
			return a;
		}
	}
}