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 Pascal (FPC 2.6.2) (judge verdict: Accepted)

var s:array[1..1000000] of char;
    i,n,b,c,min:integer;

begin
  readln(n);
  b := 0;
  c := 0;
  min := 0;
  for i:=1 to n do begin
    read(s[i]);
    if s[i]='.' then begin
      b := b + 1;
      c := c - 1;
      if min > c then min := c
      end
        else c := c + 1;
  end;
  writeln(min+b)
end.