import fractions,math,sys
from collections import Counter
n = int(input())
s = list(input())
cnt = Counter(s)
white_l = 0
black_l = 0
min = 10**9
for i in range(n):
    if s[i] == '#':
        black_l += 1
        cnt['#'] -= 1
    else:
        white_l += 1
        cnt['.'] -= 1
    if black_l + cnt['.'] < min:
        min = black_l + cnt['.']
print(min)

