Poj Solution 1113

http://poj.org/problem?id=1113

import java.io.BufferedReader; 
import java.io.IOException; 
import java.io.InputStreamReader; 

public class Main { 

    class Point { 
        int x; 
        int y; 

        public Point(int x, int y) { 
            this.x = x; 
            this.y = y; 
        } 
    } 

    public static void main(String[] args) throws IOException { 
        Main main = new Main(); 
        BufferedReader read = new BufferedReader(new InputStreamReader( 
                System.in)); 
        String[] s; 
        s = read.readLine().split(" "); 
        int n = Integer.parseInt(s[0]); 
        int l = Integer.parseInt(s[1]); 
        int x, y; 
        Point[] p = new Point[n]; 
        for (int i = 0; i < n; i++) { 
            s = read.readLine().split(" "); 
            x = Integer.parseInt(s[0]); 
            y = Integer.parseInt(s[1]); 
            p[i] = main.new Point(x, y); 
        } 
        Point[] ch = new Point[n]; 
        int len = 0; 
        if (n >= 3) { 
            len = Graham_scan(p, ch, n); 
        } 
        double sum = 0; 
        for (int i = 0; i < len - 1; i++) { 
            sum += distance(ch[i], ch[i + 1]); 
        } 
        if (len > 1) { 
            sum += distance(ch[len - 1], ch[0]); 
        } 
        sum += 2 * l * Math.PI; 
        System.out.println(Math.round(sum)); 

    } 

    public static double multiply(Point p1, Point p2, Point p0) { 
        return ((p1.x - p0.x) * (p2.y - p0.y) - (p2.x - p0.x) * (p1.y - p0.y)); 
    } 

    public static double distance(Point p1, Point p2) { 
        return (Math.sqrt((p1.x - p2.x) * (p1.x - p2.x) + (p1.y - p2.y) 
                * (p1.y - p2.y))); 
    } 

    public static int Graham_scan(Point[] PointSet, Point[] ch, int n) { 
        int i, j, k = 0, top = 2; 
        Point tmp; 
        for (i = 1; i < n; i++) 
            if ((PointSet[i].y < PointSet[k].y) 
                    || ((PointSet[i].y == PointSet[k].y) && (PointSet[i].x < PointSet[k].x))) 
                k = i; 
        tmp = PointSet[0]; 
        PointSet[0] = PointSet[k]; 
        PointSet[k] = tmp; 
        for (i = 1; i < n - 1; i++) { 
            k = i; 
            for (j = i + 1; j < n; j++) 
                if ((multiply(PointSet[j], PointSet[k], PointSet[0]) > 0) 
                        || ((multiply(PointSet[j], PointSet[k], PointSet[0]) == 0) && (distance( 
                                PointSet[0], PointSet[j]) < distance( 
                                PointSet[0], PointSet[k])))) 
                    k = j; 
            tmp = PointSet[i]; 
            PointSet[i] = PointSet[k]; 
            PointSet[k] = tmp; 
        } 
        ch[0] = PointSet[0]; 
        ch[1] = PointSet[1]; 
        ch[2] = PointSet[2]; 
        for (i = 3; i < n; i++) { 
            while (top > 0 && multiply(PointSet[i], ch[top], ch[top - 1]) >= 0) 
                top--; 
            ch[++top] = PointSet[i]; 
        } 
        return top + 1; 
    } 
}