import java.util.Scanner;


class ConvexHull{


    public static int loadPoints(int maxPoints, double[] xVal, double[] yVal){
    Scanner scan = new Scanner(System.in);
    System.out.println("Input: ");
    double num = 0;
    int counter = 0;
    boolean alter = false;


    while (scan.hasNext()) {

        num = scan.nextDouble();
        if (num < 0) {
            return counter;
        }
        if (counter > 2*maxPoints ) return counter;
        if (alter){
                yVal[counter] = num;
                counter++;
                alter = false;
            } else {
                xVal[counter] = num;
                alter = true;
            }

    }

    return counter;
    }
/*public static boolean checkDuplicates(int pointCount, double xVal[], double yVal[]){

/*    public static void computeConvexHull(int pointCount, double xVal[], double yVal[]){

    double m, c;
 put your code here


    for (int i=pointCount; i>=1; i--) {
        for (int j=0; j<i; j++) {
            if(i != j) {
                if(xVal[i] == xVal[j] && yVal[i] == yVal[j]) {
                    System.out.println("Error: There are duplicates.")
                    return true;
                }
            }

        }
    }
    return false;
    }
*/


    public static void main(String[] args) {

    int maxPoints = 70;
    double xVal[] = new double[maxPoints];
    double yVal[] = new double[maxPoints];

    int pointCount = loadPoints(maxPoints, xVal, yVal);
    System.out.println(pointCount);


    for (int i=0; i < maxPoints; i++) {
        if (xVal[i] != 0) {
            System.out.println("("+ xVal[i] + "," + yVal[i] +")");
        }
    }
   // if ( checkDuplicates(pointCount, xVal, yVal) ) return;
    }
}