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 JavaScript (node.js v5.12) (judge verdict: Runtime Error)

function C(x) {
    x = x.split("\n");
    N = x[0], S = x[1];
    
    var Wcount = 0, Bcount = 0, ans = 0;
    for (let i = 0; i < N; i++) if (S[i] === '.') Wcount++;
    // console.log(`${Wcount}`);
    for (let i = 0; i < N; i++) {
        if(S[i] === '.') Wcount--; 
        else Bcount++;
        // console.log(`${Wcount}:${Bcount}`);
        if(!ans) ans = Wcount + Bcount;
        else if(ans > Wcount + Bcount) ans = Wcount + Bcount;
    }
    console.log(`${ans}`);
    
    // console.log(`${N} ${S}`);
}
C(require("fs").readFileSync("/dev/stdin", "utf8"));