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: Wrong Answer)

var s,t:char;
    n,i,b,w,ans:integer;
begin
  readln(n);
  s:='.';
  b:=0; w:=0;
  ans:=0;
  for i:=1 to n do begin
    read(t);
    if (s=t) and (t='#') then inc(b);
    if (s=t) and (t='.') then inc(w);
    if (s<>t) and (t='#') then begin
      if b<w then inc(ans,b)
      else inc(ans,w);
      b:=1;
      w:=0
    end;
    if (s<>t) and (t='.')then inc(w);
    s:=t
  end;
  if (t='.')and(b>w) then inc(ans,w) else inc(ans,b);
  write(ans)
    
end.