Problem:
Score : 300 points

Problem Statement

There are N stones arranged in a row. Every stone is painted white or black.
A string S represents the color of the stones. The i-th stone from the left is white if the i-th character of S is ., and the stone is black if the character is #.

Takahashi wants to change the colors of some stones to black or white so that there will be no white stone immediately to the right of a black stone.
Find the minimum number of stones that needs to be recolored.

Constraints

1 \leq N \leq 2\times 10^5

S is a string of length N consisting of . and #.

Input

Input is given from Standard Input in the following format:

N
S

Output

Print the minimum number of stones that needs to be recolored.

Sample Input 1

3
#.#

Sample Output 1

1

It is enough to change the color of the first stone to white.

Sample Input 2

5
#.##.

Sample Output 2

2

Sample Input 3

9
.........

Sample Output 3

0

Solution in PyPy3 (7.3.0) (judge verdict: Wrong Answer)

n = int(input())
s = list(str(input()))
B = [0]*(n+1)
W = [0]*(n+1)

for i in range(n):
    B[i+1] = B[i]
    if s[i] == '#':
        B[i+1] += 1

s.reverse()
for i in range(n):
    W[i+1] = W[i]
    if s[i] == '.':
        W[i+1] += 1

B += [B[-1]]
W += [W[-1]]

ans = 10**18
for i in range(-1, n+1):
    ans = min(B[i+1]+W[n-i], ans)
print(ans)