n = int(input())
s = input()

# the number of '#'
p0 = s.count('#')

# the number of '.'
p1 = n - p0

p_min = min(p0, p1)

wb_ = 0
bw_ = 0
for i in range(n):

    if s[i] == '.':
        bw = bw_ 
        wb = p1
    else:
        bw = bw_ + 1
        wb = p1 - 1
    
    p_min = min(p_min, (bw + wb))

print(p_min)