public static void main ( String [ ] args ) throws IOException {
  FastReader sc = new FastReader ( ) ;
  PrintWriter out = new PrintWriter ( System . out ) ;
  int t = sc . nextInt ( ) ;
  int k = sc . nextInt ( ) ;
  double x1 = sc . nextDouble ( ) ;
  double y1 = sc . nextDouble ( ) ;
  double len = 0 ;
  while ( t -- > 1 ) {
    double x2 = sc . nextDouble ( ) ;
    double y2 = sc . nextDouble ( ) ;
    len += Math . sqrt ( Math . pow ( x2 - x1 , 2 ) + Math . pow ( y2 - y1 , 2 ) ) ;
    x1 = x2 ;
    y1 = y2 ;
  }
  out . println ( ( len / 50 ) * k ) ;
  out . close ( ) ;
}

public static void main ( String [ ] args ) throws IOException { FastReader sc = new FastReader ( ) ; PrintWriter out = new PrintWriter ( System . out ) ; int t = sc . nextInt ( ) ; int k = sc . nextInt ( ) ; double x1 = sc . nextDouble ( ) ; double y1 = sc . nextDouble ( ) ; double len = 0 ; while ( t -- > 1 ) { double x2 = sc . nextDouble ( ) ; double y2 = sc . nextDouble ( ) ; len += Math . sqrt ( Math . pow ( x2 - x1 , 2 ) + Math . pow ( y2 - y1 , 2 ) ) ; x1 = x2 ; y1 = y2 ; } out . println ( ( len / 50 ) * k ) ; out . close ( ) ; }
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