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 Kotlin (1.0.0) (judge verdict: Accepted)

fun readInts() = readLine()!!.split(" ").map(String::toInt)

fun main(args: Array<String>) {
  val n = readLine()!!.toInt()
  val xs = readInts()
  val max = xs.max()!!
  val min = xs.min()!!
  val outputs = mutableListOf<String>()

  fun processAllPos() {
    for (i in 1..(n - 1)) {
      outputs.add("$i ${i + 1}")
    }
  }

  fun processAllNeg() {
    for (i in n downTo 2) {
      outputs.add("$i ${i - 1}")
    }
  }

  if (min >= 0) {
    processAllPos()
  } else if (max <= 0) {
    processAllNeg()
  } else {
    if (Math.abs(max) >= Math.abs(min)) {
      val maxIndex = xs.indexOf(max) + 1
      for (i in 1..n) {
        outputs.add("$maxIndex $i")
      }
      processAllPos()
    } else {
      val minIndex = xs.indexOf(min) + 1
      for (i in 1..n) {
        outputs.add("$minIndex $i")
      }
      processAllNeg()
    }
  }
  println(outputs.size)
  outputs.forEach { println(it) }
}