def Run_Length_Encoding(S):
    """ランレングス圧縮

    S:文字列
    """
    if not S:
        return []

    R=[[S[0],1]]

    for i in range(1,len(S)):
        if R[-1][0]==S[i]:
            R[-1][1]+=1
        else:
            R.append([S[i],1])

    return R
#==================================================
N=int(input())
S=list(input())

a=0
ans=0
for i in range(N-1,-1,-1):
    if S[i]=="#":
        a+=1
        ans=N-1-i+a
    else:
        a=max(a-1,0)

print(ans)