num = int(input())
a = input()
count = 0
for i in range(num):
  if i < num-2 and a[i] == "#" and a[i+1] == ".":
    count += 1
    a = a[:i+1] + "#" + a[i+2:]
  elif i == num-2 and a[i] == "#" and a[i+1] == ".":
    count += 1
    a = a[:i+1] + "#"
print(count)