Contest Duration: - (local time) (100 minutes) Back to Home
C - Stones /

Time Limit: 2 sec / Memory Limit: 1024 MB

### 問題文

N 個の石が一列に並んでおり、すべての石は白か黒で塗られています。 石の状態は長さ N の文字列 S で表され、Si 文字目が . のとき左から i 個目の石が白であり、# のとき左から i 個目の石が黒であることを表します。

### 制約

• 1 \leq N \leq 2\times 10^5
• S., # のみからなる長さ N の文字列である

### 入力

N
S


### 入力例 1

3
#.#


### 出力例 1

1


### 入力例 2

5
#.##.


### 出力例 2

2


### 入力例 3

9
.........


### 出力例 3

0


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