N = int(input())
stones = input()
pre_word = stones[0]
stones_list =[]
counter = 0

for i in range(N):
    stones_list.append(stones[i])

for i in range(N):
    present_word = stones_list[i]
    if pre_word == '#' and present_word =='.':
        counter += 1
    pre_word = stones_list[i]

if '#' not in stones_list:
    print(0)
else:
    print(counter)