N = gets.chomp.to_i
S = gets.chomp
 
w = 0
b = 0
bstart = -1
bend = -1
 
for x in 0...N
  if S[x] == "."
    w += 1
    bend = -1
  else
    if bstart == -1
      bstart = x
    end
    if bend == -1
      bend = x
    end
    b += 1
  end
end
 
if bend == -1
  bend = N
end
 
if w == 0 || b == 0
  puts 0
  exit
end
 
w2 = w - bstart
#b2 = b - (N-bend)
#answer = [w2,b2].min
answer = w2
a = w2
 
for x in bstart ... bend
  if S[x] == "#"
    a += 1
  else
    a -= 1
    answer = [a,answer].min
  end
end
 
puts answer