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 (2.3.3) (judge verdict: Accepted)

n = gets.to_i
a = gets.split.map(&:to_i)

def f(a, x, y)
  a[y] += a[x]
  puts [x + 1, y + 1] * " "
end

p n * 2
amax = a.max
amin = a.min
# p amax
# p amin
if amax.abs >= amin.abs
  prev = a.index(amax)
  n.times do |i|
    f(a, prev, i)
    # prev = i
    # p a
  end
  # p a
  prev = a.index(a.max)
  n.times do |i|
    f(a, prev, i)
    prev = i
  end
else
  prev = a.index(amin)
  (n - 1).downto(0) do |i|
    f(a, prev, i)
    # prev = i
  end
  prev = a.index(a.min)
  (n - 1).downto(0) do |i|
    f(a, prev, i)
    prev = i
  end
end

# p a