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()

def counting(seq, s):
  return seq.count(s)

base_count = S.count(".#")

S = S.replace(".#", "")

idx_list = [0, len(S)]
for i in range(len(S)-1):
  if S[i] == "." and S[i+1] == "#":
    idx_list.append(i)

count_list = []
for i in idx_list:
  count_list.append(counting(S[:i], "#") + counting(S[i:], "."))
count_list.append(counting(S, "#")+0)
print(min(count_list) + base_count)