import sys
input = sys.stdin.readline
import sys
sys.setrecursionlimit(10**7)
def main():
  n=int(input())
  s=input()
  sw,sb=[0],[0]
  w,b=0,0
  for si in s:
    if si=='#':
      b+=1
    else:
      w+=1
    sw.append(w)
    sb.append(b)
  ans=n
  for i in range(n+1):
    ans=min(ans,sb[n]-sb[i]+sw[i])
  print(ans)
if __name__=='__main__':
  main()
  