# -*- coding: utf-8 -*-
n = int(input())
s = str(input())
s = s.replace(".", "0").replace('#', "1")
b = s.find("1")
a = 0
for i in range(b, n):
    a+=int(s[i])
s = [int(n) for n in s]
sums = sum(list(s))
print(min(sums, n-sums, n-b-a))