public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  double cx = sc . nextDouble ( ) ;
  double cy = sc . nextDouble ( ) ;
  int N = sc . nextInt ( ) ;
  double [ ] x = new double [ N + 2 ] ;
  double [ ] y = new double [ N + 2 ] ;
  for ( int i = 0 ;
  i < N ;
  i ++ ) {
    x [ i ] = sc . nextDouble ( ) ;
    y [ i ] = sc . nextDouble ( ) ;
  }
  double min = 100000000 ;
  for ( int i = 0 ;
  i < N - 1 ;
  i ++ ) {
    double l = dist ( x [ i ] , x [ i + 1 ] , y [ i ] , y [ i + 1 ] , cx , cy ) ;
    min = Math . min ( l , min ) ;
  }
  double l = dist ( x [ N - 1 ] , x [ 0 ] , y [ N - 1 ] , y [ 0 ] , cx , cy ) ;
  min = Math . min ( l , min ) ;
  System . out . println ( min ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; double cx = sc . nextDouble ( ) ; double cy = sc . nextDouble ( ) ; int N = sc . nextInt ( ) ; double [ ] x = new double [ N + 2 ] ; double [ ] y = new double [ N + 2 ] ; for ( int i = 0 ; i < N ; i ++ ) { x [ i ] = sc . nextDouble ( ) ; y [ i ] = sc . nextDouble ( ) ; } double min = 100000000 ; for ( int i = 0 ; i < N - 1 ; i ++ ) { double l = dist ( x [ i ] , x [ i + 1 ] , y [ i ] , y [ i + 1 ] , cx , cy ) ; min = Math . min ( l , min ) ; } double l = dist ( x [ N - 1 ] , x [ 0 ] , y [ N - 1 ] , y [ 0 ] , cx , cy ) ; min = Math . min ( l , min ) ; System . out . println ( min ) ; }
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