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++14 (GCC 5.4.1) (judge verdict: Runtime Error)

#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
int main(){
    int n,dpw[100001]={},dpb[100001]={},ans=1000000;
    char s[100100];
    scanf("%d",&n);
    scanf("%s",s);
    for(int i=0;i<n;i++){
        dpw[i+1]=dpw[i];
        if(s[i]=='#'){
            dpw[i+1]++;
        }
    }
    for(int i=n-1;i>=0;i--){
        dpb[n-i]=dpb[n-1-i];
        if(s[i]=='.'){
            dpb[n-i]++;
        }
    }
    for(int i=0;i<=n;i++){
        ans=min(ans,dpb[i]+dpw[n-i]);
    }
    printf("%d\n",ans);
}