public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  int N = sc . nextInt ( ) ;
  int M = sc . nextInt ( ) ;
  boolean [ ] [ ] rlist = new boolean [ N ] [ N ] ;
  for ( int i = 0 ;
  i < M ;
  i ++ ) {
    int x = sc . nextInt ( ) - 1 ;
    int y = sc . nextInt ( ) - 1 ;
    rlist [ x ] [ y ] = true ;
    rlist [ y ] [ x ] = true ;
  }
  int r = 1 ;
  double n = Math . pow ( 2 , N ) ;
  for ( int i = 1 ;
  i < n ;
  i ++ ) {
    ArrayList < Integer > alist = new ArrayList < Integer > ( ) ;
    boolean valid = true ;
    for ( int j = 0 ;
    j < N ;
    j ++ ) {
      if ( ( 1 & i >> j ) == 1 ) {
        alist . add ( j ) ;
      }
    }
    for ( int j = 0 ;
    j < alist . size ( ) ;
    j ++ ) {
      for ( int k = j + 1 ;
      k < alist . size ( ) ;
      k ++ ) {
        if ( ! rlist [ alist . get ( j ) ] [ alist . get ( k ) ] ) {
          valid = false ;
          break ;
        }
      }
      if ( ! valid ) {
        break ;
      }
    }
    if ( valid ) {
      r = Math . max ( r , alist . size ( ) ) ;
    }
  }
  System . out . println ( r ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; int N = sc . nextInt ( ) ; int M = sc . nextInt ( ) ; boolean [ ] [ ] rlist = new boolean [ N ] [ N ] ; for ( int i = 0 ; i < M ; i ++ ) { int x = sc . nextInt ( ) - 1 ; int y = sc . nextInt ( ) - 1 ; rlist [ x ] [ y ] = true ; rlist [ y ] [ x ] = true ; } int r = 1 ; double n = Math . pow ( 2 , N ) ; for ( int i = 1 ; i < n ; i ++ ) { ArrayList < Integer > alist = new ArrayList < Integer > ( ) ; boolean valid = true ; for ( int j = 0 ; j < N ; j ++ ) { if ( ( 1 & i >> j ) == 1 ) { alist . add ( j ) ; } } for ( int j = 0 ; j < alist . size ( ) ; j ++ ) { for ( int k = j + 1 ; k < alist . size ( ) ; k ++ ) { if ( ! rlist [ alist . get ( j ) ] [ alist . get ( k ) ] ) { valid = false ; break ; } } if ( ! valid ) { break ; } } if ( valid ) { r = Math . max ( r , alist . size ( ) ) ; } } System . out . println ( r ) ; }
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