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
a = gets.split.map &:to_i

#b = a.map.with_index{|t,i| [i+1,t.to_i]}.sort{|a,b| a[1]<=>b[1]}

acl = 1
if a.min>=0 then
  acl = 1
elsif a.max<=0 then
  acl = -1
elsif a.max.abs<=a.min.abs then
  acl = -1
end

ans = []

(2*n).times{
  b = a.sort{|a,b|(b<=>a)*acl}
  
  index = 0
  if acl == 1 then
    while a[-index-1] == b[index]&&index<n
      index += 1
    end
  else
    while a[index] == b[index]&&index<n
      index += 1
    end
  end
  
  
  #p b,a
  break if index >= n
  
  y = (acl == 1)?(n-index-1):(index)
  x = a.rindex(b[index])
  a[y] += a[x]
  #p [x+1,y+1]
  xx,yy = ans[-1]
  #p ans[-1]
  if x+1==xx && y+1==yy then
    acl*=-1
  end
  ans<<[x+1,y+1]
}

p ans.size
ans.each{|t| puts t*' '}

#p a