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

R=n
wait=-1
for i in range(n-1,-1,-1):
  if s[i]=='#':
    dx=R-i-1
    if wait-dx>=0:
      R=R-1
      wait=wait-dx+1
    else:
      R=i
      wait=0
    L=i
    
print(n-L+wait)