n = int(input())
s = input()
#white
i=0
numw=0
while s[i]==".":
    numw+=1
    i+=1
    if i == n:
        break
#  ..##.#..
w = s.count(".")
answ = w-numw

#black
j=-1
numb=0
while s[j]=="#":
    numb+=1
    j-=1
    if j*(-1) == n:
        break
b = s.count('#')
ansb=b-numb

#b&w
bw=0
k=numw-1
if k!=0:
    while s[k]=="#":
        k+=1
        bw+=1
        if k==n:
            break
wb=0
l=numb*(-1)-1
if l!=-1:
    while s[l]==".":
        l-=1
        wb+=1
        if l==n*(-1):
            break
ans3=bw+wb

print(min(ansb,answ,ans3))
