/* package whatever; // don't place package name! */
 
class M{
  static int c(int n, int p){
    int r = n,
        i = 0;
    for(; i < p; r -= n + ++i);
    return r;
  }
 
  static int d(int n, int p){
    return n - p*n + p*~p / 2;
  }
 
  public static void main(String[] a){
    System.out.println(c(2, 3));
    System.out.println(c(100, 5));
    System.out.println(c(42, 0));
    System.out.println(c(0, 3));
    System.out.println(c(0, 0));
    System.out.println();
    System.out.println(d(2, 3));
    System.out.println(d(100, 5));
    System.out.println(d(42, 0));
    System.out.println(d(0, 3));
    System.out.println(d(0, 0));
  }
}

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