// The alternative (x + y) / 2 fails for large values.
    // The alternative (x + y) >>> 1 fails for negative values.
    return (x & y) + ((x ^ y) >> 1);
  }

  /*
   * This bitmask is used as an optimization for cheaply testing for divisibility by 2, 3, or 5.
   * Each bit is set to 1 for all remainders that indicate divisibility by 2, 3, or 5, so

w,??vreser,wetomer,?e&butuoyhtiw,ciffo-sndnyd,d:-morf,o&celgoog,n&il.srebmem,neve.&1-&su,ue,?2-&su,ue,?3-&su,ue,?4-&su,ue,????,erf&-sndnyd,sndd,?filflahevres,g&arots-77ndc,de-yltsaf,nahcxeevres,?i&hcet-a-si,p-sekil,?k&auqevres,irtsretnuocevres,?l&bitpa-no,googhtiw,?m&agevres,ina-otni-si,oh-&sndnyd,ta-sndnyd,??n&-morf,ilno&-evreser,ysrab,?og-si,?r&alfduolcyrt,ehwynanohtyp:.ue,,ihcec,?srun-a-si,t&i&nuarepo,s&-ybboh,aloy,elpmis,rodabew,tipohs,xiw,??omer-sndnyd,upmocsma,ysgolb,?v&als-elcibuc-a-si,i&...

w,??vreser,wetomer,?e&butuoyhtiw,ciffo-sndnyd,d:-morf,o&celgoog,n&il.srebmem,neve.&1-&su,ue,?2-&su,ue,?3-&su,ue,?4-&su,ue,????,erf&-sndnyd,sndd,?filflahevres,g&arots-77ndc,de-yltsaf,nahcxeevres,?i&hcet-a-si,p-sekil,?k&auqevres,irtsretnuocevres,?l&bitpa-no,googhtiw,?m&agevres,ina-otni-si,oh-&sndnyd,ta-sndnyd,??n&-morf,ilno&-evreser,ysrab,?og-si,?r&alfduolcyrt,ehwynanohtyp:.ue,,ihcec,?srun-a-si,t&i&nuarepo,s&-ybboh,aloy,elpmis,rodabew,tipohs,xiw,??omer-sndnyd,upmocsma,ysgolb,?v&als-elcibuc-a-si,i&...