public static void main ( String [ ] args ) {
  Scanner in = new Scanner ( System . in ) ;
  int n = in . nextInt ( ) ;
  int k = in . nextInt ( ) ;
  int a = in . nextInt ( ) ;
  int b = in . nextInt ( ) ;
  double ans = 0 ;
  for ( int i = 1 ;
  i < n ;
  i ++ ) {
    int c = in . nextInt ( ) ;
    int d = in . nextInt ( ) ;
    ans += Math . abs ( Math . sqrt ( ( a - c ) * ( a - c ) + ( b - d ) * ( b - d ) ) ) ;
    a = c ;
    b = d ;
  }
  System . out . println ( ( ans * k / 50 ) ) ;
  in . close ( ) ;
}

public static void main ( String [ ] args ) { Scanner in = new Scanner ( System . in ) ; int n = in . nextInt ( ) ; int k = in . nextInt ( ) ; int a = in . nextInt ( ) ; int b = in . nextInt ( ) ; double ans = 0 ; for ( int i = 1 ; i < n ; i ++ ) { int c = in . nextInt ( ) ; int d = in . nextInt ( ) ; ans += Math . abs ( Math . sqrt ( ( a - c ) * ( a - c ) + ( b - d ) * ( b - d ) ) ) ; a = c ; b = d ; } System . out . println ( ( ans * k / 50 ) ) ; in . close ( ) ; }
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