public static void main ( String [ ] args ) throws IOException {
  BufferedReader br = new BufferedReader ( new InputStreamReader ( System . in ) ) ;
  PrintWriter pw = new PrintWriter ( System . out ) ;
  StringTokenizer st = new StringTokenizer ( br . readLine ( ) ) ;
  int a = Integer . parseInt ( st . nextToken ( ) ) ;
  int tA = Integer . parseInt ( st . nextToken ( ) ) ;
  st = new StringTokenizer ( br . readLine ( ) ) ;
  int b = Integer . parseInt ( st . nextToken ( ) ) ;
  int tB = Integer . parseInt ( st . nextToken ( ) ) ;
  String timing = br . readLine ( ) ;
  int hrs = Integer . parseInt ( timing . substring ( 0 , 2 ) ) ;
  int mins = Integer . parseInt ( timing . substring ( 3 ) ) ;
  int simDeparture = hrs * 60 + mins ;
  int simArrival = simDeparture + tA ;
  int counter = 0 ;
  for ( int i = 300 ;
  i < 1440 ;
  i += b ) {
    int busDeparture = i ;
    int busArrival = i + tB ;
    if ( busDeparture >= simArrival || simDeparture >= busArrival ) continue ;
    counter ++ ;
  }
  pw . println ( counter ) ;
  pw . flush ( ) ;
  pw . close ( ) ;
}

public static void main ( String [ ] args ) throws IOException { BufferedReader br = new BufferedReader ( new InputStreamReader ( System . in ) ) ; PrintWriter pw = new PrintWriter ( System . out ) ; StringTokenizer st = new StringTokenizer ( br . readLine ( ) ) ; int a = Integer . parseInt ( st . nextToken ( ) ) ; int tA = Integer . parseInt ( st . nextToken ( ) ) ; st = new StringTokenizer ( br . readLine ( ) ) ; int b = Integer . parseInt ( st . nextToken ( ) ) ; int tB = Integer . parseInt ( st . nextToken ( ) ) ; String timing = br . readLine ( ) ; int hrs = Integer . parseInt ( timing . substring ( 0 , 2 ) ) ; int mins = Integer . parseInt ( timing . substring ( 3 ) ) ; int simDeparture = hrs * 60 + mins ; int simArrival = simDeparture + tA ; int counter = 0 ; for ( int i = 300 ; i < 1440 ; i += b ) { int busDeparture = i ; int busArrival = i + tB ; if ( busDeparture >= simArrival || simDeparture >= busArrival ) continue ; counter ++ ; } pw . println ( counter ) ; pw . flush ( ) ; pw . close ( ) ; }
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