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 Ruby (2.7.1) (judge verdict: Accepted)

class Problem
  attr_accessor *(?a..?z).to_a.map(&:to_sym)
  def initialize
    @n = gets.to_s.to_i
    @a = gets.split.map(&:to_i)
    @ans = []
  end

  def base
    minv = a.min
    mini = a.index(minv)
    maxv = a.max
    maxi = a.index(maxv)
    if minv.abs < maxv.abs
      return maxi, maxv
    else
      return mini, minv
    end
  end

  def add(x,y)
    @ans << [x+1,y+1].join(" ")
    a[y] += a[x]
  end

  def solve
    i, v = base
    n.times do |j|
      next if i == j
      add(i,j)
    end

    if v < 0
      (n-1).downto(1) do |i|
        add(i,i-1)
      end
    else
      0.upto(n-2) do |i|
        add(i,i+1)
      end
    end
    @ans
  end

  def show(ans)
    puts ans.size
    ans.each do |s|
      puts s
    end
  end
end

Problem.new.instance_eval do
  show(solve)
end