I=input
N=int(I())
S=I()
l=[N]
for c in S:l+=[[0,l[-1]+1][c>'#']]
r=[N]
for c in S[::-1]:r+=[[0,r[-1]+1][c>'#']]
o=0
for i in range(N):
	t=min(l[1+i],r[N-i])
	if o<t:o,a=t,i
print(a+1)