N=int(input())
S=input()
tmp=1
L=[]
ans=10**6
black=0
white=0
for i in range(1,len(S)):
    if S[i]==S[i-1]:
        tmp+=1
    else:
        L.append(tmp)
        tmp=1
    if i ==len(S)-1:
        L.append(tmp)

    if S[i]=='#':
        black+=1
    else:
        white+=1
cul=[0]*(len(L)+2)
for i in range(len(L)):
    cul[i+2]=L[i]+cul[i-2]


if S[0]=='.':
    for i in range(2,len(cul)):
        if i%2==0:
            ans=min(ans,cul[i-1]+white-cul[i])
        else:
            ans=min(ans,cul[i]+white-cul[i-1])
else:
    for i in range(2,len(cul)):
        if i % 2 == 0:
            ans = min(ans,cul[i]+white-cul[i-1])
        else:
            ans = min(ans,cul[i-1]+white-cul[i])


if len(L)==1:
    ans=0
else:
    ans=min(ans,sum(L[0::2]),sum(L[1::2]))

print(ans)