import java.util.Vector;

public class TestSum {
  private Vector<Vector<Integer>> vv;
  public TestSum() {
    vv = new Vector<Vector<Integer>>();
  }
  public void populate(int numElem) {
    Vector<Integer> v = new Vector<Integer>();
    vv.add(v);
    for (int i = 0; i < numElem; i++) {
      v.add(i);
    }
  }
  public int sum() {
    int acc = 0;
    Vector<Integer> v = vv.elementAt(vv.size() - 1);
    for (int i = v.size() - 1; i > 0; i--) {
      acc += v.get(i);
      v.removeElementAt(i);
    }
    return acc;
  }
  public static void main(String args[]) {
    if (args.length != 1) {
      System.err.println("Syntax: java ObjCreator num_objs");
      System.exit(1);
    }
    TestSum ts = new TestSum();
    long acc = 0;
    int numObj = Integer.parseInt(args[0]);
    for (int i = 0; i < numObj; i++) {
      ts.populate(2);
      acc += ts.sum();
    }
    System.out.println(acc);
  }
}