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: Runtime Error)


#include <stdio.h>

int main(){
	int n;
	int kuro=0,siro=0,ans,i,p1,p2;
	char s[20002]="";
	if(scanf("%d ",&n)!=1)return 1;
	if(scanf("%s",s)!=1)return 1;
	
	for(i=0;i<n;i++){
		if(s[i]=='#'){
			kuro++;
		}else if(s[i]=='.'){
			if(kuro)siro++;
		}
	}
	p1=siro;
	siro=kuro=0;
	for(i=n-1;i>=0;i--){
		if(s[i]=='#'){
			if(siro)kuro++;
		}else if(s[i]=='.'){
			siro++;
		}
	}
	p2=kuro;
	if(p1<p2){
		ans=p1;
	}else{
		ans=p2;
	}
	printf("%d\n",ans);
	return 0;
}