Problem:
Score : 600 points

Problem Statement

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.

Sample Input 1

3
-2 5 -1

Sample Output 1

2
2 3
3 3

After the first operation, a = (-2,5,4).

After the second operation, a = (-2,5,8), and the condition is now satisfied.

Sample Input 2

2
-1 -3

Sample Output 2

1
2 1

After the first operation, a = (-4,-3) and the condition is now satisfied.

Sample Input 3

5
0 0 0 0 0

Sample Output 3

0

The condition is satisfied already in the beginning.

Solution in Java8 (OpenJDK 1.8.0) (judge verdict: Accepted)

import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Scanner;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 *
 * @author mikit
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        DNonDecreasing solver = new DNonDecreasing();
        solver.solve(1, in, out);
        out.close();
    }

    static class DNonDecreasing {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            int n = in.nextInt();
            out.println(2 * n - 1);

            int max = 0;
            int index = 0;
            for (int i = 0; i < n; i++) {
                int a = in.nextInt();
                if (Math.abs(max) < Math.abs(a)) {
                    max = a;
                    index = i;
                }
            }
            for (int i = 0; i < n; i++) {
                out.print(index + 1);
                out.print(' ');
                out.println(i + 1);
            }

            if (max < 0) {
                for (int i = n; i > 1; i--) {
                    out.print(i);
                    out.print(' ');
                    out.println(i - 1);
                }
            } else {
                for (int i = 1; i < n; i++) {
                    out.print(i);
                    out.print(' ');
                    out.println(i + 1);
                }
            }
        }

    }
}