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 (Clang 3.8.0) (judge verdict: Wrong Answer)

#include <stdio.h>
int main(){
    int n,i,count,mode,mode2,bc,bc2,bc3;
    char s[200001];
    count = mode = mode2 = bc = bc2 = bc3 = 0;
    scanf("%d",&n);
    scanf("%s",s);
    for (i = 0; i < n; i++){
        if (s[i] == '#'){
            mode = 1;
            if (mode2 == 0){
                bc++;
            }else{
                bc2++;
            }
        }else if (mode == 1){
            count++;
            mode2 = 1;
            if (bc2 > 0){
                bc3++;
            }
        }
    }
    n = n - count;
    if (n >= count){
        printf("%d",count);
    }else {
        count = n;
        if (bc3 == 0){
            count = bc;
        }
        printf("%d",count);
    }
    return 0;
}