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 (2.4.0) (judge verdict: Wrong Answer)

import sys


def solve():
    readline = sys.stdin.buffer.readline
    mod = 10 ** 9 + 7
    n = int(readline())
    s = str(readline().rstrip().decode('utf-8'))
    w = s.count(".")
    b = 0
    mc = 10 ** 10
    for i in range(n):
        if s[i] == "#":
            b += 1
        else:
            w -= 1
        mc = min(mc, b + w)
    print(mc)


if __name__ == '__main__':
    solve()