/**
  * Copyright (c): Uwe Schmidt, FH Wedel
  *
  * You may study, modify and distribute this source code
  * FOR NON-COMMERCIAL PURPOSES ONLY.
  * This copyright message has to remain unchanged.
  *
  * Note that this document is provided 'as is',
  * WITHOUT WARRANTY of any kind either expressed or implied.
  */

/**
  *
  *        n-1
  * f(n) = sum f1(i)
  *        j=0
  */

//--------------------

public
class Sum extends Sequence {
  private
  long sum;

  private
  Sequence s;

  public
  Sum(Sequence s) {
    this.s   = s;
    this.sum = 0;
  }

  public
  long next() {
    long res = sum;

    sum += s.next();

    return res;
  }
}

//--------------------