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(void){
    int N;
    char S[100010];
    int rui[100020];
    scanf("%d",&N);
    scanf("%s",&S);
    
    int i=0;
    int count=0;
    
    while(S[i]=='.')    //一番最初から白である間
    {
        count++;
        i++;
    }
    rui[0]=count;   //白の数を格納(0でも)
    
    int j=1;  //累積和の要素番号を格納
    while(i<N)
    {
        count=0;
        while(S[i]=='#')   //黒である間
        {
            count++;
            i++;
        }
        rui[j]=count;
        j++;
        count=0;
        
        while(S[i]=='.')    //城である間
        {
            count++;
            i++;
        }
        rui[j]=count;
        j++;
        count=0;
        
    }
    
    int ans;
    if(rui[1]<=rui[2])  ans=rui[1];
    else    ans=rui[2];
    
    
    i=4;    //累積和の1番目スタート
    while(i<N)
    {
        ans+=rui[i];
        i=i+2;
    }
    
    printf("%d",ans);
    return 0;
}