N = int(input())
S = input()
c = 0
for i in range(N - 1, -1, -1):
    if S[i] == ".":
        c1 = i
        break
cc = 0
for i in range(N - 1, c1, -1):
    if S[i] == "#":
        cc += 1
a = S[:i + 1].count(".")
b = S[:i + 1].count("#")
ans = min(a, b, c2)
print(ans)