import sys
from operator import itemgetter
from collections import defaultdict, deque
import heapq
from heapq import heapify, heappop, _heapify_max, heappush
from bisect import bisect_left, bisect_right
import math
import itertools
import copy

stdin=sys.stdin
#sys.setrecursionlimit(10 ** 7)
## import pypyjit
## pypyjit.set_param('max_unroll_recursion=-1')

ip=lambda: int(sp())
fp=lambda: float(sp())
lp=lambda:list(map(int,stdin.readline().split()))
sp=lambda:stdin.readline().rstrip()
Yp=lambda:print('Yes')
Np=lambda:print('No')
inf = 1 << 60
inf = float('inf')
mod = 10 ** 9 + 7
mod = 998244353
eps = 1e-9
sortkey1 = itemgetter(0)
sortkey2 = lambda x: (x[0], x[1])



###############################################################

N = ip()
S = list(sp())
S = S[::-1]
ans = -1
for i in range(N):
    if S[i] == '#':
        x = i + 1
        if x <= ans + 1:
            ans += 2
        else:
            ans = i + 1
print(ans)