public static void main ( String [ ] args ) {
  Scanner in = new Scanner ( System . in ) ;
  int n = in . nextInt ( ) ;
  int [ ] p1 = new int [ n ] ;
  int [ ] p2 = new int [ n ] ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) p1 [ i ] = in . nextInt ( ) - 1 ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) p2 [ in . nextInt ( ) - 1 ] = i ;
  int prev = - 1 ;
  int i ;
  for ( i = 0 ;
  i < n && p2 [ p1 [ i ] ] > prev ;
  i ++ ) {
    prev = p2 [ p1 [ i ] ] ;
  }
  System . out . println ( n - i ) ;
}

public static void main ( String [ ] args ) { Scanner in = new Scanner ( System . in ) ; int n = in . nextInt ( ) ; int [ ] p1 = new int [ n ] ; int [ ] p2 = new int [ n ] ; for ( int i = 0 ; i < n ; i ++ ) p1 [ i ] = in . nextInt ( ) - 1 ; for ( int i = 0 ; i < n ; i ++ ) p2 [ in . nextInt ( ) - 1 ] = i ; int prev = - 1 ; int i ; for ( i = 0 ; i < n && p2 [ p1 [ i ] ] > prev ; i ++ ) { prev = p2 [ p1 [ i ] ] ; } System . out . println ( n - i ) ; }
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