public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  final Coord A = new Coord ( sc . nextInt ( ) , sc . nextInt ( ) ) ;
  final Coord B = new Coord ( sc . nextInt ( ) , sc . nextInt ( ) ) ;
  final int N = sc . nextInt ( ) ;
  Coord [ ] c = new Coord [ N ] ;
  for ( int i = 0 ;
  i < N ;
  i ++ ) {
    c [ i ] = new Coord ( sc . nextInt ( ) , sc . nextInt ( ) ) ;
  }
  sc . close ( ) ;
  int count = 0 ;
  for ( int i = 0 ;
  i < N ;
  i ++ ) {
    if ( isIntersect ( A . x , A . y , B . x , B . y , c [ i ] . x , c [ i ] . y , c [ ( i + 1 ) % N ] . x , c [ ( i + 1 ) % N ] . y ) ) {
      count ++ ;
    }
  }
  System . out . println ( count / 2 + 1 ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; final Coord A = new Coord ( sc . nextInt ( ) , sc . nextInt ( ) ) ; final Coord B = new Coord ( sc . nextInt ( ) , sc . nextInt ( ) ) ; final int N = sc . nextInt ( ) ; Coord [ ] c = new Coord [ N ] ; for ( int i = 0 ; i < N ; i ++ ) { c [ i ] = new Coord ( sc . nextInt ( ) , sc . nextInt ( ) ) ; } sc . close ( ) ; int count = 0 ; for ( int i = 0 ; i < N ; i ++ ) { if ( isIntersect ( A . x , A . y , B . x , B . y , c [ i ] . x , c [ i ] . y , c [ ( i + 1 ) % N ] . x , c [ ( i + 1 ) % N ] . y ) ) { count ++ ; } } System . out . println ( count / 2 + 1 ) ; }
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