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.*;
import java.util.*;

class Main {
    static Scanner scanner = new Scanner();

    public static void main(String[]$) {
        int n = scanner.nextInt();
        int max = 0;
        int maxIndex = 0;
        int[] a = new int[n];
        for (int i = 0; i < n; i++) {
            a[i] = scanner.nextInt();
            if (Math.abs(max) < Math.abs(a[i])) {
                max = a[i];
                maxIndex = i;
            }
        }
        List<Point> ans = new ArrayList<>();
        for (int i = 0; i < n; i++) {
            if (maxIndex != i) {
                ans.add(new Point(maxIndex + 1, i + 1));
            }
        }
        if (max == 0) {
            System.out.println(0);
            return;
        } else if (max > 0) {
            for (int i = 2; i <= n; i++) {
                ans.add(new Point(i - 1, i));
            }
        } else {
            for (int i = n - 1; i > 0; i--) {
                ans.add(new Point(i + 1, i));
            }
        }
        System.out.println(ans.size());
        for (Point point : ans) {
            System.out.println(point.x + " " + point.y);
        }
    }

    static class Scanner {
        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in), 1 << 15);
        StringTokenizer tokenizer;

        String next() {
            try {
                while (tokenizer == null || !tokenizer.hasMoreTokens()) {
                    tokenizer = new StringTokenizer(reader.readLine());
                }
            } catch (IOException ignored) {
            }
            return tokenizer.nextToken();
        }

        int nextInt() {
            return Integer.parseInt(next());
        }

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