import sys
sys.setrecursionlimit(10**6)
from math import floor,ceil,sqrt,factorial,log
from heapq import heappop, heappush, heappushpop
from collections import Counter,defaultdict,deque
from itertools import accumulate,permutations,combinations,product,combinations_with_replacement
from bisect import bisect_left,bisect_right
from copy import deepcopy
from operator import itemgetter
from fractions import gcd
mod = 10 ** 9 + 7
inf = float('inf')
ninf = -float('inf')
 
#整数input
def ii(): return int(sys.stdin.readline().rstrip()) #int(input())
def mii(): return map(int,sys.stdin.readline().rstrip().split())
def limii(): return list(mii()) #list(map(int,input().split()))
def lin(n:int): return [ii() for _ in range(n)]
def llint(n: int): return [limii() for _ in range(n)]
#文字列input
def ss(): return sys.stdin.readline().rstrip() #input()
def mss(): return sys.stdin.readline().rstrip().split()
def limss(): return list(mss()) #list(input().split())
def lst(n:int): return [ss() for _ in range(n)]
def llstr(n: int): return [limss() for _ in range(n)]

#本当に貪欲法か？ DP法では？？
#本当に貪欲法か？ DP法では？？
#本当に貪欲法か？ DP法では？？

n=ii()
s=list(ss())

mat=Counter(s)
black=mat["#"]
white=n-black

ans=10**100

if black==0 or white==0:
    print(0)
    exit()
if s[-1]=="#" and black==1:
    print(0)
    exit()

tmptowhite=0

for i in range(n):
    if s[i]=="#":
        tmptowhite+=1
    lefttowhite=tmptowhite
    righttoblack=white -(i+1-tmptowhite)
    ans=min(lefttowhite+righttoblack,ans)
    #print(tmptowhite,lefttowhite,righttoblack)
print(ans)

