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()

ans1 = 0
ans2 = 0
idx1 = 1e9
idx2 = 1e9

for i, ele in enumerate(s):
  if ele=="#":
    idx1 = i
    break

for i, ele in enumerate(s[::-1]):
  if ele==".":
    idx2 = i
    break

if idx1<len(s):
  for ele in s[idx1::]:
    if ele==".":
      ans1 += 1

if idx2<len(s):
  for ele in s[idx2::-1]:
    if ele=="#":
      ans2 += 1

print(min(ans1, ans2))