}
    },
    /** Works for all nonnegative signed longs. */
    LARGE {
      /** Returns (a + b) mod m. Precondition: {@code 0 <= a}, {@code b < m < 2^63}. */
      private long plusMod(long a, long b, long m) {
        return (a >= m - b) ? (a + b - m) : (a + b);
      }

      /** Returns (a * 2^32) mod m. a may be any unsigned long. */
      private long times2ToThe32Mod(long a, long m) {

      }
    },
    /** Works for all nonnegative signed longs. */
    LARGE {
      /** Returns (a + b) mod m. Precondition: {@code 0 <= a}, {@code b < m < 2^63}. */
      private long plusMod(long a, long b, long m) {
        return (a >= m - b) ? (a + b - m) : (a + b);
      }

      /** Returns (a * 2^32) mod m. a may be any unsigned long. */
      private long times2ToThe32Mod(long a, long m) {