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)

MOD=10**9+7
cnt=0; sum=0; prev=nil; can=true; h=Hash.new(0)
def gs() gets.chomp end
def gi() gets.to_i end
def gsmi() gets.chomp.split.map(&:to_i) end

def desc(ar) ar.sort!{|x,y|y<=>x} end
def min(a,b) a<=b ? a : b end
def max(a,b) a>=b ? a : b end
def sum(ar) ar.inject(:+) end

def bs(ar,eq,n) en=(eq==1 ? :>= : :>); ar.bsearch_index{|x|x.send(en,n)} end
def C(a,b) b==0||a==b ? 1 : (b=a-b if a/2<b;(a-b+1..a).inject(:*)/(1..b).inject(:*)) end

def puts_yesno(can) puts(can ? 'Yes' : 'No') end
def putsend(s) puts s; exit end
def debug(k,v) puts "#{k}:#{v}" end
########### ( ˘ω˘ )ｽﾔｧ… ###########
n=gi
a=gsmi

max=0
max_i=0
n.times do |i|
  abs=a[i].abs
  if abs>max
    max=abs
    max_i=i
  end
end

ans=[]
if a[max_i]>=0
  # 全部正にする
  n.times do |i|
    if a[i]<0
      a[i]+=a[max_i]
      ans<<[max_i+1,i+1]
    end
  end

  prev= -1
  n.times do |i|
    if a[i]<prev
      a[i]+=prev
      ans<<[i,i+1]
    end
    prev=a[i]
  end
else
  # 全部負にする
  n.times do |i|
    if a[i]>0
      a[i]+=a[max_i]
      ans<<[max_i+1,i+1]
    end
  end

  prev= 1
  (n-1).downto(0) do |i|
    if a[i]>prev
      a[i]+=prev
      ans<<[i+2,i+1]
    end
    prev=a[i]
  end
end

putsend 0 if ans.size.zero?
puts ans.size
ans.each{|i|puts i.join(" ")}