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 = list(input())
xx = []
ten = []
count = 0#最初
count1 = 0 
count2 = 1
count3 = 0
count4 = 0
count5 = 0
for i in S:
    if i=="#" and count==0:
        count1 += 1
        count = 1
       
    elif i =="#" and count2==1 and count==1:
        count1 += 1
        
    elif i =="." and count2==1 and count==1:
        xx.append(count1)
        count1 = 1
        count2 = 0
        
    elif i =="." and count2==0 and count==1:
        count1 += 1

    elif i=="#" and count2==0 and count==1:
        ten.append(count1)
        count1 = 1
        count2 = 1


if count2==0 and count1>=1:
    ten.append(count1)

for i in range(len(xx)):
    if (xx[i]+count5)>=ten[i]:
        count3 += ten[i]
        count5 += ten[i]+xx[i]
    else:
        count3 += xx[i]
        count5 = 0
count4 = sum(xx)
if count3 > count4:
    count3 = count4
        
print(count3)