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>
 
int main(void){
	int N,i,count=0,flag=2;
	char S[200000];
	scanf("%d \n %s",&N,S);
	for(i=0;i<N;i++){
		if(S[i]=='#' && S[i+1]=='.'){
			if(i >= N/2){
					flag=0; //基準点以降 黒にする場合
				}else{
					flag=1; //基準点以降 白にする場合
				}
				i++;
				break;
		}
	}
	
	for(;i<N;i++){
		if(flag==0 && S[i]=='.'){ //基準点以降の白の数をカウントする
			count++;
		}
		if(flag==1 && S[i]=='#'){ //基準点以降の黒の数をカウントする
			count++;
		}
	}
			
	printf("%d",count);
	return 0;
}