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)

io = STDIN
$n=io.gets.to_i
a=io.gets.split.map(&:to_i)
def pp(a,max)
  ix=a.index(max)
  puts "#{ix.next} 1"
  (1..$n).each_cons(2){|i,j|puts "#{i} #{j}"}
end
def mm(a,min)
  ix=a.index(min)
  puts "#{ix.next} #{$n}"
  (1..$n).to_a.reverse.each_cons(2){|i,j|puts "#{i} #{j}"}
end
def max2all(a,max)
  ix=a.index(max)
  (1..$n).map{|i|puts "#{ix.next} #{i}"}
  a.map{|i|i+max}
end
def min2all(a,min)
  ix=a.index(min)
  (1..$n).map{|i|puts "#{ix.next} #{i}"}
  a.map{|i|i+min}
end
max,min=a.max,a.min
if min==max
  puts 0
elsif min>=0
  puts $n
  pp(a,max)
elsif max<=0
  puts $n
  mm(a,min)
elsif min.abs < max.abs
  puts 2*$n
  a=max2all(a,max)
  pp(a,a.max)
else
  puts 2*$n
  a=min2all(a,min)
  mm(a,a.min)
end