public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int n = sc . nextInt ( ) , m = sc . nextInt ( ) , p = sc . nextInt ( ) , q = sc . nextInt ( ) ;
  int arr1 [ ] [ ] = new int [ n ] [ 2 ] ;
  int arr2 [ ] [ ] = new int [ m ] [ 2 ] ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    for ( int j = 0 ;
    j < 2 ;
    j ++ ) {
      arr1 [ i ] [ j ] = sc . nextInt ( ) ;
    }
  }
  for ( int i = 0 ;
  i < m ;
  i ++ ) {
    for ( int j = 0 ;
    j < 2 ;
    j ++ ) {
      arr2 [ i ] [ j ] = sc . nextInt ( ) ;
    }
  }
  int ans = 0 ;
  for ( int k = p ;
  k <= q ;
  k ++ ) {
    z : for ( int i = 0 ;
    i < m ;
    i ++ ) {
      int aa = arr2 [ i ] [ 0 ] + k ;
      int bb = arr2 [ i ] [ 1 ] + k ;
      for ( int j = 0 ;
      j < n ;
      j ++ ) {
        if ( aa >= arr1 [ j ] [ 0 ] && bb <= arr1 [ j ] [ 1 ] || aa >= arr1 [ j ] [ 0 ] && aa <= arr1 [ j ] [ 1 ] || bb >= arr1 [ j ] [ 0 ] && bb <= arr1 [ j ] [ 1 ] || aa <= arr1 [ j ] [ 0 ] && bb >= arr1 [ j ] [ 1 ] ) {
          ans ++ ;
          break z ;
        }
      }
    }
  }
  System . out . println ( ans ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int n = sc . nextInt ( ) , m = sc . nextInt ( ) , p = sc . nextInt ( ) , q = sc . nextInt ( ) ; int arr1 [ ] [ ] = new int [ n ] [ 2 ] ; int arr2 [ ] [ ] = new int [ m ] [ 2 ] ; for ( int i = 0 ; i < n ; i ++ ) { for ( int j = 0 ; j < 2 ; j ++ ) { arr1 [ i ] [ j ] = sc . nextInt ( ) ; } } for ( int i = 0 ; i < m ; i ++ ) { for ( int j = 0 ; j < 2 ; j ++ ) { arr2 [ i ] [ j ] = sc . nextInt ( ) ; } } int ans = 0 ; for ( int k = p ; k <= q ; k ++ ) { z : for ( int i = 0 ; i < m ; i ++ ) { int aa = arr2 [ i ] [ 0 ] + k ; int bb = arr2 [ i ] [ 1 ] + k ; for ( int j = 0 ; j < n ; j ++ ) { if ( aa >= arr1 [ j ] [ 0 ] && bb <= arr1 [ j ] [ 1 ] || aa >= arr1 [ j ] [ 0 ] && aa <= arr1 [ j ] [ 1 ] || bb >= arr1 [ j ] [ 0 ] && bb <= arr1 [ j ] [ 1 ] || aa <= arr1 [ j ] [ 0 ] && bb >= arr1 [ j ] [ 1 ] ) { ans ++ ; break z ; } } } } System . out . println ( ans ) ; }
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