public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  long A = sc . nextLong ( ) ;
  long B = sc . nextLong ( ) ;
  if ( A == B ) {
    System . out . println ( 1 ) ;
  }
  else {
    int abi = 62 ;
    for ( ;
    abi >= 0 ;
    abi -- ) if ( ( ( A ^ B ) & ( 1l << abi ) ) != 0 ) break ;
    long mask = ( 1l << abi ) - 1 ;
    long ans = mask - ( A & mask ) + 1 ;
    int bi = abi - 1 ;
    for ( ;
    bi >= 0 ;
    bi -- ) if ( ( ( 1l << bi ) & B ) != 0 ) break ;
    long temp = 1l << ( bi + 1 ) ;
    ans += temp + ( 1l << abi ) - Math . max ( temp , A & mask ) ;
    System . out . println ( ans ) ;
  }
  sc . close ( ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; long A = sc . nextLong ( ) ; long B = sc . nextLong ( ) ; if ( A == B ) { System . out . println ( 1 ) ; } else { int abi = 62 ; for ( ; abi >= 0 ; abi -- ) if ( ( ( A ^ B ) & ( 1l << abi ) ) != 0 ) break ; long mask = ( 1l << abi ) - 1 ; long ans = mask - ( A & mask ) + 1 ; int bi = abi - 1 ; for ( ; bi >= 0 ; bi -- ) if ( ( ( 1l << bi ) & B ) != 0 ) break ; long temp = 1l << ( bi + 1 ) ; ans += temp + ( 1l << abi ) - Math . max ( temp , A & mask ) ; System . out . println ( ans ) ; } sc . close ( ) ; }
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