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>
#include<string.h>
int main(){
    int n;
    char *s;
    int i;
    int alpha=0;
    int beta=0;
    scanf("%d",&n);
    s=(char*)malloc(sizeof(char)*n*2);
    scanf("%s",s);
    for(i=0;i<n-2;i++){
        if(s[i]=='#'){
            beta++;
        }
    }
    for(i=1;i<n;i++){
        if(s[i]=='.' && s[i-1]=='#'){
            s[i]='#';
            alpha++;
        }
    }
    // printf("alpha=%d beta=%d\n",alpha,beta);
    if(alpha<beta){
        printf("%d\n",alpha);
    }else{
        printf("%d\n",beta);
    }
    return 0;
}