N = gets.to_i
A = gets.split.map(&:to_i)
O = (0 ... N).sort_by{|i| A[i] }
used = Array.new(N)
T = N.times.map do |i| 
  if O[i] != i && A[O[i]] != A[i] && !used[i] 
    used[i] = used[O[i]] = true
    "#{i} #{O[i]}"
  else
    nil
  end
end
T.compact!
puts T.size
puts T
$stdout.flush
gets
exit(0)