public static void main ( String [ ] args ) throws IOException {
  byte n = Byte . parseByte ( in . readLine ( ) ) ;
  String [ ] l ;
  int p , q , rooms = 0 ;
  while ( n -- > 0 ) {
    l = in . readLine ( ) . split ( "\\s" ) ;
    p = Byte . parseByte ( l [ 0 ] ) ;
    q = Byte . parseByte ( l [ 1 ] ) ;
    if ( q - p > 1 ) {
      rooms ++ ;
    }
  }
  out . print ( rooms ) ;
  out . close ( ) ;
}

public static void main ( String [ ] args ) throws IOException { byte n = Byte . parseByte ( in . readLine ( ) ) ; String [ ] l ; int p , q , rooms = 0 ; while ( n -- > 0 ) { l = in . readLine ( ) . split ( " \\ s " ) ; p = Byte . parseByte ( l [ 0 ] ) ; q = Byte . parseByte ( l [ 1 ] ) ; if ( q - p > 1 ) { rooms ++ ; } } out . print ( rooms ) ; out . close ( ) ; }
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