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: Time Limit Exceeded)

n=int(input())
s=input()
cnt=float('inf')
wnum=0
bnum=0
for i in range(n+1):
  s1=s[:i]
  s2=s[i:]
#  print(s1,s2)
  wnum=s1.count('#')
  bnum=s2.count('.')
  cnt=min(cnt,wnum+bnum)

if s.count('#')==n or s.count('.')==n:
  cnt=0
  
print(cnt)