n = int(input())
s = input()
li = []
for i in range(n):
    if s[i] == "#":
        li.append(i)
li.append(len(s))
sum = 0
if len(li) == 1:
    print(0)
else:
    for i in range(len(li)-1):
        diff = li[i+1] - li[i] - 1
        if diff > i+1:
            sum = i+1
        else:
            sum += diff
    print(sum)