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)

SIRO = '.'
KURO = '#'
N = int(input())
S = input()
sLst = []
cnt = 1
if S[0] != '#':
    sLst.append(0)

for i in range(0, N - 1):
    if S[i] == S[i + 1]:
       cnt += 1
    else:
        sLst.append(cnt)
        cnt = 1
    if i == N - 2:
        sLst.append(cnt)
kCnt = 0
sCnt = 0
for i in range(0, len(sLst), 2):
    if len(sLst) >= i + 2:
        kCnt += sLst[i]
        sCnt += sLst[i + 1]
ans = min(kCnt, sCnt)
print(ans)