class Progs {

    /* 1a. */
    /** The sum of all integers, k, such that 1 <= k < N and 
     *  N is evenly divisible by k. */
    static int factorSum (int N) {
        /* *Replace the following with the answer* */
        return 0;
    }

    /* 1b. */
    /** Print the set of all sociable pairs whose members are all
     *  between 1 and N>=0 (inclusive) on the standard output (one pair per 
     *  line, smallest member of each pair first, with no repetitions). */
    static void printSociablePairs (int N) {
        /* *Fill in here* */
    }

    /* 2a. */
    /** A list consisting of the elements of A followed by the
     *  the elements of B.  May modify items of A. 
     *  Don't use 'new'. */
    static IntList dcatenate(IntList A, IntList B) {
        /* *Replace the following with the answer* */
        return null;
    }

    /* 2b. */
    /** The sublist consisting of LEN items from list L,
     *  beginning with item #START (where the first item is #0). 
     *  Does not modify the original list elements. 
     *  It is an error if the desired items don't exist. */
    static IntList sublist (IntList L, int start, int len) {
        /* *Replace the following with the answer* */
        return null;
    }

    /* 2c. */
    /** The sublist consisting of LEN items from list L,
     *  beginning with item #START (where the first item is #0). 
     *  May modify the original list elements. Don't use 'new'.
     *  It is an error if the desired items don't exist. */
    static IntList dsublist (IntList L, int start, int len) {
        /* *Replace the following with the answer* */
        return null;
    }

}