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)

N = int(input())
S = input().rstrip()
index = S.find("#")
answer = 0
if index == -1:
    print(0)
    exit()
else:
    answer = S[index:].count(".")
index = S.rfind(".")
if index == -1:
    print(0)
    exit()
else:
    answer = S[:index+1].count("#") if S[:index+1].count("#")<answer else answer
index_s = S.rfind("#")
S_new1 = S[:index_s]
S_new1 = S[:S_new1.rfind(".")+1]
S_new2 = S[index-1:]
res = S_new2.count(".") + S_new1.count("#")
answer = res if res < answer else answer
print(answer)