rem: (1<<34)-1, (1<<41)-1, (1<<48)-1, (1<<55)-1 };
add: (1LL<<34)-1, (1LL<<41)-1, (1LL<<48)-1, (1LL<<55)-1 };
context: static inline longlong	readVLSInt(MatroskaFile *mf) {  static longlong bias[8] = { (1<<6)-1, (1<<13)-1, (1<<20)-1, (1<<27)-1,			      (1<<34)-1, (1<<41)-1, (1<<48)-1, (1<<55)-1 };  int	    m;  longlong  v = readVLUIntImp(mf,&m);  return v - bias[m];}