public static void main ( String arg [ ] ) {
  Scanner sc = new Scanner ( System . in ) ;
  int r = sc . nextInt ( ) ;
  int x1 = sc . nextInt ( ) ;
  int y1 = sc . nextInt ( ) ;
  int x2 = sc . nextInt ( ) ;
  int y2 = sc . nextInt ( ) ;
  double dis = 1.0 * Math . sqrt ( 1.0 * ( x2 - x1 ) * ( x2 - x1 ) + 1.0 * ( y2 - y1 ) * ( y2 - y1 ) ) ;
  long res = ( long ) Math . ceil ( dis / ( 2 * r ) ) ;
  System . out . println ( res ) ;
}

public static void main ( String arg [ ] ) { Scanner sc = new Scanner ( System . in ) ; int r = sc . nextInt ( ) ; int x1 = sc . nextInt ( ) ; int y1 = sc . nextInt ( ) ; int x2 = sc . nextInt ( ) ; int y2 = sc . nextInt ( ) ; double dis = 1.0 * Math . sqrt ( 1.0 * ( x2 - x1 ) * ( x2 - x1 ) + 1.0 * ( y2 - y1 ) * ( y2 - y1 ) ) ; long res = ( long ) Math . ceil ( dis / ( 2 * r ) ) ; System . out . println ( res ) ; }
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