public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int p = sc . nextInt ( ) ;
  int q = sc . nextInt ( ) ;
  int l = sc . nextInt ( ) ;
  int r = sc . nextInt ( ) ;
  int [ ] a = new int [ p ] ;
  int [ ] b = new int [ p ] ;
  int [ ] c = new int [ q ] ;
  int [ ] d = new int [ q ] ;
  for ( int i = 0 ;
  i < p ;
  i ++ ) {
    a [ i ] = sc . nextInt ( ) ;
    b [ i ] = sc . nextInt ( ) ;
  }
  for ( int i = 0 ;
  i < q ;
  i ++ ) {
    c [ i ] = sc . nextInt ( ) ;
    d [ i ] = sc . nextInt ( ) ;
  }
  int count = 0 , strt , end ;
  boolean flag ;
  for ( int i = l ;
  i <= r ;
  i ++ ) {
    flag = false ;
    for ( int j = 0 ;
    j < q ;
    j ++ ) {
      strt = c [ j ] + i ;
      end = d [ j ] + i ;
      for ( int k = 0 ;
      k < p ;
      k ++ ) {
        if ( strt > b [ k ] || end < a [ k ] ) {
          continue ;
        }
        else {
          count ++ ;
          flag = true ;
          break ;
        }
      }
      if ( flag == true ) {
        break ;
      }
    }
  }
  System . out . println ( count ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int p = sc . nextInt ( ) ; int q = sc . nextInt ( ) ; int l = sc . nextInt ( ) ; int r = sc . nextInt ( ) ; int [ ] a = new int [ p ] ; int [ ] b = new int [ p ] ; int [ ] c = new int [ q ] ; int [ ] d = new int [ q ] ; for ( int i = 0 ; i < p ; i ++ ) { a [ i ] = sc . nextInt ( ) ; b [ i ] = sc . nextInt ( ) ; } for ( int i = 0 ; i < q ; i ++ ) { c [ i ] = sc . nextInt ( ) ; d [ i ] = sc . nextInt ( ) ; } int count = 0 , strt , end ; boolean flag ; for ( int i = l ; i <= r ; i ++ ) { flag = false ; for ( int j = 0 ; j < q ; j ++ ) { strt = c [ j ] + i ; end = d [ j ] + i ; for ( int k = 0 ; k < p ; k ++ ) { if ( strt > b [ k ] || end < a [ k ] ) { continue ; } else { count ++ ; flag = true ; break ; } } if ( flag == true ) { break ; } } } System . out . println ( count ) ; }
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