n = gets.chomp.to_i
s = gets.chomp

a = []
(0...n).each do |i|
  a << i if s[i] == '#'
end

if a.empty?
  puts 0

else
  w = []
  w[0] = a[0] == 0 ? 0 : s[0, a[0] - 1].count('#')
  (1...a.length).each do |i|
    w[i] = w[i - 1] + s[a[i - 1], a[i] - a[i - 1]].count('#')
  end

  b = []
  b[a.length - 1] = s[a[-1], n - a[-1]].count('.')
  (a.length - 2).downto(0).each do |i|
    b[i] = b[i + 1] + s[a[i], a[i + 1] - a[i]].count('.')
  end

  counts = []
  (0...a.length).each do |i|
    counts[i] = w[i] + b[i]
  end
  counts << s.counts('#')

  puts counts.min
end
