N=int(input())
S=input()
before=''
count=0
count_list=[]
w_count_list=[0]
b_count_list=[0]
for i,moji in enumerate(S):
    count+=1
    if moji!=before:
        if i!=0:
            count_list.append(count-1)
            if before=='.':
                w_count_list.append(w_count_list[-1]+count-1)
            else:
                b_count_list.append(b_count_list[-1]+count-1)
            count=1 
            before=moji
    if i==len(S)-1:
        count_list.append(count)
        if moji=='.':
            w_count_list.append(w_count_list[-1]+count)
        else:
            b_count_list.append(b_count_list[-1]+count)
cand=[]
ki=0
if S[0]=='.':
    count_list=count_list[1:]
    length=len(count_list)
    if length%2==1:
        ki=1
    for i in range(length//2+1):
        cand.append(w_count_list[-1]-w_count_list[i]+b_count_list[-1]-b_count_list[max_num+ki-i])
else:
    length=len(count_list)
    if length%2==1:
        ki=1
    max_num=length//2
    for i in range(length//2+1):
        cand.append(w_count_list[-1]-w_count_list[i]+b_count_list[-1]-b_count_list[max_num+ki-i])
        #print(length-i*2-ki)
        #print(count_list[i*2+1::2])
print(min(cand))
#print(cand)