public static void main ( String [ ] args ) {
  Scanner scan = new Scanner ( System . in ) ;
  int n = scan . nextInt ( ) ;
  int k = scan . nextInt ( ) ;
  double s = 0 ;
  int tx = 0 ;
  int ty = 0 ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    int x = scan . nextInt ( ) ;
    int y = scan . nextInt ( ) ;
    if ( i > 0 ) {
      s += Math . sqrt ( ( ( x - tx ) * ( x - tx ) ) + ( ( y - ty ) * ( y - ty ) ) ) ;
    }
    tx = x ;
    ty = y ;
  }
  double result = ( k * s ) / 50 ;
  System . out . println ( result ) ;
}

public static void main ( String [ ] args ) { Scanner scan = new Scanner ( System . in ) ; int n = scan . nextInt ( ) ; int k = scan . nextInt ( ) ; double s = 0 ; int tx = 0 ; int ty = 0 ; for ( int i = 0 ; i < n ; i ++ ) { int x = scan . nextInt ( ) ; int y = scan . nextInt ( ) ; if ( i > 0 ) { s += Math . sqrt ( ( ( x - tx ) * ( x - tx ) ) + ( ( y - ty ) * ( y - ty ) ) ) ; } tx = x ; ty = y ; } double result = ( k * s ) / 50 ; System . out . println ( result ) ; }
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