n = int(input())
s = input()
flag = 0
location1 = 0
location2 = n
for i in range(n):
    #    print(s[i])
    if s[i] == '#':
        location1 = i
        flag = 1
        break

i = 0

for i in range(n):
    #    print(s[n-i-1])
    if s[n-i-1] == '.':
        location2 = n - i - 1
        flag = 2
        break


if flag == 0:
    print(0)
else:
    print(min(s[location1:n].count('.'), s[0:location2].count('#')))