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 min(int m,int n){
    if(m>n) return n;
    else return m;
}

int main(void){
    int n;
    scanf("%d",&n);
    char s[201000],t[201000];
    scanf("%s",s);
    int cnt1=0,cnt2=0;
    strcpy(t,s);
    while(1){
        int ch=0;
        for(int i=0;i<n-1;i++){
            if(s[i]=='#'&&s[i+1]=='.'){
                s[i]='.';
                cnt1++;
                ch=1;
        	}
        }
        if(ch==0)break;
    }
    while(1){
        int ch=0;
        for(int i=0;i<n-1;i++){
            if(t[i]=='#'&&t[i+1]=='.'){
                t[i+1]='#';
                cnt2++;
                ch=1;
        	}
        }
        if(ch==0)break;
    }
    printf("%d",min(cnt1,cnt2));
    return 0;
}