N=int(input())
s=input()
s=[s[i] for i in range(len(s))]
hit1=0
count1=0
for i in s:
    if i=="#":
        hit1 = 1
    if i==".":
        count1=count1+hit1
        
count2=0
hit2=0
for i in range(len(s)):
    if s[-1-i]==".":
        hit2 = 1
    if s[-1-i]=="#":
        count2=count2+hit2
        
print(min(count1,count2))