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 Python (3.4.3) (judge verdict: Runtime Error)

import sys

a = []
for l in sys.stdin:
    a.append(l)

num = int(a[0])
haichi = a[1]
count_list = []

# 左側を全部白にする手数 (= 左側の黒の数)
split_left_count = [sum([x == '#' for x in haichi[:i]]) for i, k in enumerate(haichi)]

# 右側を全部黒にする手数 (= 右側の白の数)
split_right_count = [sum([x == '.' for x in haichi[i:]]) for i, k in enumerate(haichi)]

black_all_count = sum([x == '#' for x in haichi])
white_all_count = sum([x == '.' for x in haichi])

black_count = 0
for i in range(num):
    each_haichi = haichi[i]
    if each_haichi == '#':
        
    count_list.append(split_left_count[i]+split_right_count[i])

print(min(count_list))