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 C (GCC 5.4.1) (judge verdict: Wrong Answer)

#include <stdio.h>
 
char S[200000];
 
void Do(int N){
  int i, n, clb, crb, crw, csw, bbb, wbb, www, m;
  scanf("%s", S);
  clb = crb = crw = csw = 0;
  for(i = N - 1;i >= 0;i--){
    if(S[i] == '#') csw++;
    else break;
    N--;
  }
  for(i = 0;i < N;i++){
    if(S[i] == '.') clb++;
    else{
      n = i;
      for(i = n + 1;i < N;i++){
	if(S[i] == '#') crw++;
	else crb++;
      }
    }
  }
  bbb = clb + crb;
  if(csw == 0) wbb = crb;
  else wbb = 1e9;
  www = crw + 1 + csw;
  if(bbb > wbb){
    if(wbb > www) m = www;
    else m = wbb;
  }else{
    if(bbb > www) m = www;
    else m = bbb;
  }
  printf("%d\n", m);
}

int main(void){
  int N;
  scanf("%d", &N);
  Do(N);
  return 0;
}