public static void main ( String [ ] args ) {
  FastReader fs = new FastReader ( ) ;
  StringBuilder sb = new StringBuilder ( ) ;
  int t = fs . nextInt ( ) ;
  int k = fs . nextInt ( ) ;
  int prevX = 0 ;
  int prevY = 0 ;
  int currX = 0 ;
  int currY = 0 ;
  double sum = 0 ;
  for ( int tt = 0 ;
  tt < t ;
  tt ++ ) {
    if ( tt == 0 ) {
      prevX = fs . nextInt ( ) ;
      prevY = fs . nextInt ( ) ;
    }
    else {
      currX = fs . nextInt ( ) ;
      currY = fs . nextInt ( ) ;
      sum += dist ( currX , prevX , currY , prevY ) ;
      prevX = currX ;
      prevY = currY ;
    }
  }
  System . out . println ( k * sum / 50.0 ) ;
}

public static void main ( String [ ] args ) { FastReader fs = new FastReader ( ) ; StringBuilder sb = new StringBuilder ( ) ; int t = fs . nextInt ( ) ; int k = fs . nextInt ( ) ; int prevX = 0 ; int prevY = 0 ; int currX = 0 ; int currY = 0 ; double sum = 0 ; for ( int tt = 0 ; tt < t ; tt ++ ) { if ( tt == 0 ) { prevX = fs . nextInt ( ) ; prevY = fs . nextInt ( ) ; } else { currX = fs . nextInt ( ) ; currY = fs . nextInt ( ) ; sum += dist ( currX , prevX , currY , prevY ) ; prevX = currX ; prevY = currY ; } } System . out . println ( k * sum / 50.0 ) ; }
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