sclass GlobalID {
  // We need 76 bits for 26^16 IDs
  long a;
  int b;
  
  *() {}
  *(S id) {
    assertGlobalID(id);
    BigInt value = 0;
    for (int i = 0; i < l(id); i++)
      value = plus(mul(value, 26), charDiff(id.charAt(i), 'a'));
    a = value.longValue();
    value = value.shiftRight(64);
    b = value.intValue();
  }
  
  toString {
    BigInt value = b;
    value = value.shiftLeft(32);
    value = plus(value, (a >> 32) & 0xFFFFFFFF);
    value = value.shiftLeft(32);
    value = plus(value, a & 0xFFFFFFFF);
    StringBuilder buf = new StringBuilder(16);
    for (int i = 0; i < 16; i++) {
      buf.append(charPlus('a', mod(value, 26)).intValue());
      value = div(value, 26);
    }
    ret str(buf);
  }
}