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>
#include <stdlib.h>

int main(void) {
   
   int N;
   
   scanf("%d",&N);
   
   char *S = malloc(sizeof(char)*(N+100));
   
   scanf("%s",S);
   
   int i;
   int flag = 0;
   int count1 = 0;
   
   for(i = 0;i < N;i++){
      if(flag == 1){
         if(S[i] == '.'){
            count1++;
         }
      }
      else {
         if(S[i] == '#'){
            flag = 1;
         }
      }
   }
   
   int count2 = 0;
   
   for(i = 0;i < N;i++){
      if(S[i] == '#'){
         count2++;
      }
   }
   
   if(count1 < count2) {
      printf("%d\n",count1);
   }
   else {
      printf("%d\n",count2);
   }
      
   return 0;
}