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;
	char S[2*10*10*10*10*10];
	int i;
	int B[2*10*10*10*10*10]={0};
	int W[2*10*10*10*10*10]={0};
	int ans=2*10*10*10*10*10;
	int myself=0;
	scanf("%d %s",&N,S);
	
	
	
	for(i=N-2;i>=0;i--){
		if(S[i+1]=='#'){
			B[i]=B[i+1]+1;
			W[i]=W[i+1];
		}else {
			W[i]=W[i+1]+1;
			B[i]=B[i+1];
		}
	}
	if(B[0]==0){
		printf("0");
		return 0;
	}
	for(i=0;i<N;i++){
		if(S[i]=='#'){
			if(ans>W[i]+myself){
				ans=W[i]+myself;
			}
			myself++;
		}
	
	}
	
	printf("%d",ans);
	
	
	
	
	
	return 0;
}