public static void main ( String [ ] args ) {
  Scanner s = new Scanner ( System . in ) ;
  int n = s . nextInt ( ) ;
  int m = s . nextInt ( ) ;
  int k = s . nextInt ( ) ;
  int a [ ] = new int [ n ] ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) a [ i ] = s . nextInt ( ) ;
  m = m - 1 ;
  int min = Integer . MAX_VALUE , min1 = Integer . MAX_VALUE ;
  for ( int j = 0 ;
  j < m ;
  j ++ ) {
    if ( k >= a [ j ] && a [ j ] != 0 ) {
      if ( ( m - j ) < min ) min = m - j ;
    }
  }
  for ( int j1 = m + 1 ;
  j1 < n ;
  j1 ++ ) {
    if ( k >= a [ j1 ] && a [ j1 ] != 0 ) {
      if ( ( j1 - m ) < min1 ) min1 = j1 - m ;
    }
  }
  int p = Math . min ( min , min1 ) ;
  System . out . println ( p * 10 ) ;
}

public static void main ( String [ ] args ) { Scanner s = new Scanner ( System . in ) ; int n = s . nextInt ( ) ; int m = s . nextInt ( ) ; int k = s . nextInt ( ) ; int a [ ] = new int [ n ] ; for ( int i = 0 ; i < n ; i ++ ) a [ i ] = s . nextInt ( ) ; m = m - 1 ; int min = Integer . MAX_VALUE , min1 = Integer . MAX_VALUE ; for ( int j = 0 ; j < m ; j ++ ) { if ( k >= a [ j ] && a [ j ] != 0 ) { if ( ( m - j ) < min ) min = m - j ; } } for ( int j1 = m + 1 ; j1 < n ; j1 ++ ) { if ( k >= a [ j1 ] && a [ j1 ] != 0 ) { if ( ( j1 - m ) < min1 ) min1 = j1 - m ; } } int p = Math . min ( min , min1 ) ; System . out . println ( p * 10 ) ; }
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