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 Scala (2.11.7) (judge verdict: Accepted)

import java.io._
import java.util.StringTokenizer
import scala.util.control.Breaks.{breakable,break}

object Main extends App {
  val in = new InputReader(System.in)
  val pw = new PrintWriter(System.out)

  val N = in.next().toInt
  val a = new Array[Int](N)

  for (i <- 0 until N) {
    a(i) = in.next().toInt
  }

  var mx = a.max
  var mn = a.min

  def printer(ans: List[(Int, Int)]): Unit = {
    pw.println(ans.length)
    for (e <- ans)
      pw.println(s"${e._1} ${e._2}")
    pw.flush()
  }

  var ans: List[(Int, Int)] = List()

  if (Math.abs(mx) == 0 && Math.abs(mn) == 0) {
    println(0)
  }
  else if (Math.abs(mx) > Math.abs(mn)) {
    var ind = 0
    for (i <- 0 until N) {
      if(a(i) == mx)
        ind = i
    }

    for (i <- 0 until N) {
      ans = (ind+1, i+1) :: ans
    }

    for(i <- 1 until N) {
      ans = (i-1+1, i+1) :: ans
    }

    printer(ans.reverse)
  }
  else {
    var ind = 0
    for (i <- 0 until N) {
      if(a(i) == mn)
        ind = i
    }

    for (i <- 0 until N) {
      ans = (ind+1, i+1) :: ans
    }

    for(i <- (0 until N-1).reverse) {
      ans = (i+1+1, i+1) :: ans
    }

    printer(ans.reverse)
  }
}


class InputReader(stream: InputStream) {
  private val reader = new BufferedReader(new InputStreamReader(stream))
  private var tokenizer: StringTokenizer = new StringTokenizer(reader.readLine())
  def next(): String = {
    while (!tokenizer.hasMoreTokens()) {
      tokenizer = new StringTokenizer(reader.readLine())
    }
    tokenizer.nextToken()
  }
}