n = gets.to_i
s = gets.chomp.split("")
bw = []
i = cnt = 0
jud = s[0]
s.each do |c|
  if jud == c
    cnt += 1
  else
    bw[i] = cnt
    jud = c
    i += 1
    cnt = 1
  end
end
bw[i] = cnt

min = 999999999999
bsums = Array.new(i+2)
wsums = Array.new(i+2)
bsums[0] = 0
wsums[0] = 0
i = 1
le = 0
le = 1 if s[0] == "."
bw.each do |k|
  if i % 2 == le
    bsums[i] = bsums[i-1] + k
    wsums[i] = wsums[i-1]
  else
    wsums[i] = wsums[i-1] + k
    bsums[i] = bsums[i-1]
  end
  i += 1
end
for j in 0..(i-1)
  ch = bsums[j] + (wsums[i-1] - wsums[j])
  min = ch if min > ch
end
puts min