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: Wrong Answer)

def remove_fwhite(S):
    fwhite = 0
    for fw in S:
        if fw == '.':
            fwhite += 1
        else:
            break
    return fwhite

def remove_fblack(S):
    fblack = 0
    for fb in S[::-1]:
        if fb == '#':
            fblack += 1
        else:
            break
    return fblack

def count_stone(S):
    black = 0
    white = 0
    for stone in S:
        if stone == '#':
            black += 1
        else:
            white += 1
    print(min(black,white))

N = int(input())
S = str(input())

fw = remove_fwhite(S)
fb = remove_fblack(S)
print(S[fw:N-fb])
if fw == 0 or fb == 0:
    count_stone(S)
else:
    count_stone(S[fw:N-fb])