from functools import reduce
l = int(input())
src = list(map(lambda x: 1 if x=="." else 0, input()))
lb = 0
rw = sum(src)
a = rw
for i in range(l):
  if src[i]==0:
    lb+=1
  else:
    rw-=1
  a = min(ans, left_black + right_white)
  if ans==0:
    break
print(ans)