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 num;
    char str[20000];
    int cnt=0;
    int white_cnt=0;
    int i;
    
    scanf("%d", &num);
    scanf("%s", str);

    for(i=num-1;i>=0;i--){
        if(str[i]=='.'){
            white_cnt++;
            i--;
            break;
        }
    }
    while(i>=0){
        if(str[i]=='#'){
            cnt++;
        }
        else{
            white_cnt++;
        }
        i--;
    }
    
    printf("%d\n",cnt<white_cnt?cnt:white_cnt);
    return 0;
}