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)

from numpy import*
from itertools import*
n=int(input())
s=input()
t=s.count("#")
r=s.count(".")

l=[t,r]
x=[len(list(v))for k,v in groupby(s)if k=="#"]
y=[len(list(v))for k,v in groupby(s)if k=="."]
if len(x)>len(y):
    y=[0]+y
elif len(x)<len(y):
    x=[0]+x
else:
    y=y+[0]
    x=[0]+x

x=array([0]+list(accumulate(x)))
y=array(list(accumulate(y[::-1]))[::-1]+[0])
print(min(x+y))