import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, tan, asin, acos, atan, radians, degrees#, log2
from itertools import accumulate, permutations, combinations, combinations_with_replacement, product, groupby
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from bisect import bisect, bisect_left, insort, insort_left
from fractions import gcd
from heapq import heappush, heappop
from functools import reduce
def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
def ZIP(n): return zip(*(MAP() for _ in range(n)))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10**9 + 7
#from decimal import *

N = INT()
S = input()

ans = 0
tmp = 0
for i in range(1, N):
	if S[i] == "#" and S[i-1] == ".":
		w = 0
		flg = False
		for x in S[tmp:i]:
			if x == "#":
				flg = True
			if flg and x == ".":
				w += 1

		b = 0
		flg = False
		for x in S[tmp:i][::-1]:
			if x == ".":
				flg = True
			if flg and x == "#":
				b += 1

		ans += min(w, b)
		tmp = i
		
w = 0
flg = False
for x in S[tmp:]:
	if x == "#":
		flg = True
	if flg and x == ".":
		w += 1

b = 0
flg = False
for x in S[tmp:][::-1]:
	if x == ".":
		flg = True
	if flg and x == "#":
		b += 1

ans += min(w, b)
print(ans)