N = int(raw_input())                                                                                                                                           
S = list(raw_input())                                                                                                                                          
                                                                                                                                                               
c = 0                                                                                                                                                          
for i in range(N):                                                                                                                                             
      if S[N-1-i] == "#":                                                                                                                                      
            c += 1                                                                                                                                             
      else:                                                                                                                                                    
            break                                                                                                                                              
if c > 0:                                                                                                                                                      
      S = S[:-c]                                                                                                                                               
                                                                                                                                                               
cc = 0                                                                                                                                                         
                                                                                                                                                               
for j in range(N-c):                                                                                                                                           
      if S[j] == ".":                                                                                                                                          
            cc += 1                
if N-cc > 0:
      print(min(cc, N-c-cc))
else:
      print("0")
