challenge 169 hard

import java.util.Scanner;

public class C169H
{
    public static void main(String[] args)
    {
        Scanner in = new Scanner(System.in);
    double area;
    double total = 0;

    System.out.print("Please enter the number of vertices of the polygon: ");
    int numVertices = in.nextInt();

    double[][] vertices = new double[numVertices + 1][2];

        System.out.println("Please enter the coordinates of each vertex, separated by spaces: ");

    for(int x = 0; x < numVertices; x++)
    {
            vertices[x][0] = in.nextDouble();
            vertices[x][1] = in.nextDouble();
    }

    vertices[numVertices][0] = vertices[0][0];
    vertices[numVertices][1] = vertices[0][1];

    for(int x = 0; x < vertices.length - 1; x++)
    {
            total += ((vertices[x][0] * vertices[x + 1][1]) - (vertices[x + 1][0] * vertices[x][1]));
    }

    area = Math.abs((double)(total / 2.0));

    System.out.println("The area of the polygon is " + area + " square units.");
    }
}