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.awt.Point;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.List;
import java.util.stream.IntStream;
import java.util.stream.Stream;

public class Main {
	public static void main(String[] args) throws IOException {
		try (AtCoderReader ar = new AtCoderReader()) {
			ar.nextLine();
			int[] A = ar.nextIntArray();

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

			int max = Integer.MIN_VALUE;
			int min = Integer.MAX_VALUE;

			int maxAt = -1;
			int minAt = -1;

			for (int i = 0; i < A.length; i++) {
				int value = A[i];
				if (max < value) {
					max = value;
					maxAt = i;
				}

				if (value < min) {
					min = value;
					minAt = i;
				}

			}

			if (min >= 0 || max <= 0) {
				// aが非負整数の場合または、すべて負の整数の場合は何もしない
			} else {
				int value = min;
				int valueAt = minAt;
				if (Math.abs(max) >= Math.abs(min)) {
					value = max;
					valueAt = maxAt;
				}

				for (int i = 0; i < A.length; i++) {
					if (i != valueAt) {
						A[i] += value;
						list.add(new Point(valueAt, i));
					}
				}
				A[valueAt] += value;
				list.add(new Point(valueAt, valueAt));

				min = Integer.MAX_VALUE;
				for (int i = 0; i < A.length; i++) {
					min = Math.min(A[i], min);
				}
			}

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

	public static class AtCoderReader implements AutoCloseable {
		private final BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

		public final String[] nextStringArray() throws IOException {
			return this.br.readLine().split(" ");
		}

		public final Stream<String> nextStream() throws IOException {
			return Stream.of(this.nextStringArray());
		}

		public final IntStream nextIntStream() throws NumberFormatException, IOException {
			return this.nextStream().mapToInt(Integer::parseInt);
		}

		public final int[] nextIntArray() throws IOException {
			return this.nextIntStream().toArray();
		}

		public final int nextInt() throws NumberFormatException, IOException {
			return Integer.parseInt(nextLine());
		}

		public final String nextLine() throws IOException {
			return this.br.readLine();
		}

		@Override
		public final void close() throws IOException {
			br.close();
		}
	}
}