public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  long a = sc . nextLong ( ) ;
  long b = sc . nextLong ( ) ;
  long ans = 0 ;
  long c = 0 ;
  if ( a % 2 == 0 ) {
    if ( b % 2 == 0 ) {
      c = b - a ;
      c /= 2 ;
      if ( c % 2 == 0 ) {
        ans = b ;
      }
      else {
        ans = b ^ 1 ;
      }
    }
    else {
      c = b - a + 1 ;
      c /= 2 ;
      if ( c % 2 == 0 ) {
        ans = 0 ;
      }
      else {
        ans = 1 ;
      }
    }
  }
  else {
    if ( b % 2 == 0 ) {
      c = b - a - 1 ;
      c /= 2 ;
      if ( c % 2 == 0 ) {
        ans = a ^ b ;
      }
      else {
        ans = ( a ^ b ) ^ 1 ;
      }
    }
    else {
      c = b - a ;
      c /= 2 ;
      if ( c % 2 == 0 ) {
        ans = a ;
      }
      else {
        ans = a ^ 1 ;
      }
    }
  }
  System . out . println ( ans ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; long a = sc . nextLong ( ) ; long b = sc . nextLong ( ) ; long ans = 0 ; long c = 0 ; if ( a % 2 == 0 ) { if ( b % 2 == 0 ) { c = b - a ; c /= 2 ; if ( c % 2 == 0 ) { ans = b ; } else { ans = b ^ 1 ; } } else { c = b - a + 1 ; c /= 2 ; if ( c % 2 == 0 ) { ans = 0 ; } else { ans = 1 ; } } } else { if ( b % 2 == 0 ) { c = b - a - 1 ; c /= 2 ; if ( c % 2 == 0 ) { ans = a ^ b ; } else { ans = ( a ^ b ) ^ 1 ; } } else { c = b - a ; c /= 2 ; if ( c % 2 == 0 ) { ans = a ; } else { ans = a ^ 1 ; } } } System . out . println ( ans ) ; }
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