n=int(input())
s=input()

i=0
for ss in s:
  if ss=="#":
    break
  i+=1

s=s[i:]  
  
cnt=0
while s[-1]=="#":
  s=s[:-1]
  if s=="":
    print(0)
    exit()
  
print(min(s.count("."),s.count("#")))

  