
n = int(input())
s = input()

min_num = n
white_num_left = 0
black_num_left = 0
white_num = s.count('.')
black_num = n - white_num

if white_num == 0 or white_num == n:
    print(0)
else:
    for i in range(n):
        if s[i] == '#':
            black_num_left += 1
        else:
            white_num_left += 1
        if min_num >= black_num_left + (white_num - white_num_left):
            min_num = black_num_left + (white_num - white_num_left)
    print(min_num)