stone=input()
color=input()
a=int(stone)
counter=0
counter2=0
black = 0
white = 0
xxx=[]
yyy=[]
list=[]
for i in range(a):
    list.append(color[i])
for i in range(a):
    if list[i]=='#':
        xxx.append(i)
        black += 1
    if list[i]=='.':
        yyy.append(i)
        white += 1
if white ==0 or black==0:
    print('0')
else:
    s = min(xxx)
    t = max(yyy)
    for k in range(s,a):
        if list[k]=='.' :
            counter = 1+ counter
    for j in range(0,t):
        if list[j]=='#':
            counter2 = 1 +counter2
    if counter < counter2:
        print(counter)
    else:
        print(counter2)