# frozen_string_literal: true

N = gets.to_i
AS = gets.chomp.split.map(&:to_i)

MAX = AS.max
prev = MAX
RESULT = AS.size - 1 - (0..AS.index(MAX) - 1).to_a.reverse.map do |i|
  if AS[i] + 1 == prev
    prev = AS[i]
    1
  else
    0
  end
end.sum

puts RESULT