def solve():
  N = int(input())
  S = input()
  stones = []
  look = S[0]
  cnt = 0

  if S[0] == '.': stones.append(0)
  for s in S:
    if look == s: cnt += 1
    else:
      stones.append(cnt)
      cnt = 1
      look = s
  stones.append(cnt)
  if S[N - 1] == '#': stones.append(0)

  count = sum(stones[1::2])
  ans = count

  for i in range(0, N - 2, 2):
    count = count + stones[i] - stones[i + 1]
    if ans > count: ans = count
  return ans

print(solve())