Code
=================================================================
import java.util.*;
import java.io.*;

public class t1020
{
public static void main(String[] args)
{
Scanner in = new Scanner(System.in);
PrintWriter out = new PrintWriter(System.out);

int N = in.nextInt();
Double R = in.nextDouble();

Double[] x = new Double[N];
Double[] y = new Double[N];

double len = 2 * Math.PI * R;

for(int i = 0; i < N; i ++)
{
x[i] = in.nextDouble();
y[i] = in.nextDouble();
}

for(int i = 0; i < N - 1; i ++)
len += Math.sqrt(Math.pow((x[i] - x[i == 0 ? N - 1 : i - 1]), 2) + Math.pow((y[i] - y[i == 0 ? N - 1 : i - 1]), 2));

out.println(len);
out.flush();
}
}
================================================================
Write:
================================================================
4 1.0
Exception in thread "main" java.util.InputMismatchException
at java.util.Scanner.throwFor(Unknown Source)
at java.util.Scanner.next(Unknown Source)
at java.util.Scanner.nextDouble(Unknown Source)
at t1020.main(t1020.java:12)
=================================================================
Why I can not read 1.0?!
4 1 -- Read correctly!!!