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: Wrong Answer)

N = gets.to_i
as = gets.split.map(&:to_i)

max = as.max
min = as.min
max_i = as.find_index(max)
min_i = as.find_index(min)

operations = []

if min >= 0
    negative = []
    positive = (0...N).to_a
elsif max <= 0
    negative = (0...N).to_a
    positive = []
else
    left = [min_i, max_i].min
    right = [min_i, max_i].max
    (0...left).each do |i|
        operations.push([min_i, i])
    end
    ((right+1)...N).each do |i|
        operations.push([max_i, i])
    end
    if min.abs <= max.abs
        (left..right).each do |i|
            next if i == max_i
            operations.push([max_i, i])
            negative = (0...left).to_a
            positive = (left...N).to_a
        end
    else
        (left..right).each do |i|
            next if i == max_i
            operations.push([min_i, i])
            negative = (0..right).to_a
            positive = ((left+1)...N).to_a
        end
    end
end

while negative.length > 1 do
    operations.push([negative[-1], negative[-2]])
    negative.pop
end

while positive.length > 1 do
    operations.push([positive[0], positive[1]])
    positive.shift
end

print operations.length, "\n"
operations.each do |op|
    print op[0] + 1, ' ', op[1] + 1, "\n"
end