WA了无数次，哪里错了？
import java.util.Scanner;
import java.text.*;
public class Main{
    public static void main(String[] args) {
        Scanner cin=new Scanner(System.in);
        DecimalFormat df=new DecimalFormat("#.00");
        int n=cin.nextInt();
        double r=cin.nextDouble();
        double res=0;
        double[] x=new double[n];
        double[] y=new double[n];
        x[0]=cin.nextDouble();
        y[0]=cin.nextDouble();
        for(int i=1;i<n;i++)
        {
            x[i]=cin.nextDouble();
            y[i]=cin.nextDouble();
            res+=Math.sqrt((x[i]-x[i-1])*(x[i]-x[i-1])+(y[i]-y[i-1])*(y[i]-y[i-1]));
        }
        res+=Math.sqrt((x[n-1]-x[0])*(x[n-1]-x[0])+(y[n-1]-y[0])*(y[n-1]-y[0]));
        res+=2*Math.PI*r;
        System.out.println(df.format(res));
    }
}