N = int(input())
S = list(input())
flag=(S[0]=="#")
count=0
for i in range(1,len(S)):
    if not flag:
        flag=(S[i]=="#" and S[i-1]==".")
    if flag:
        if S[i]=="." and S[i-1]=="#":
            count+=1
            S[i]="#"
print(count)