public static void main ( String [ ] args ) {
  FastReader scan = new FastReader ( ) ;
  PrintWriter rt = new PrintWriter ( System . out ) ;
  int y = scan . nextInt ( ) ;
  String s = scan . next ( ) ;
  if ( y == 1 ) {
    rt . print ( "Yes" ) ;
    rt . close ( ) ;
    return ;
  }
  else {
    int arr [ ] = new int [ 27 ] ;
    for ( int i = 0 ;
    i < s . length ( ) ;
    i ++ ) {
      arr [ s . charAt ( i ) - 97 ] ++ ;
      if ( arr [ s . charAt ( i ) - 97 ] == 2 ) {
        rt . print ( "YES" ) ;
        rt . close ( ) ;
        return ;
      }
    }
  }
  rt . print ( "NO" ) ;
  rt . close ( ) ;
  return ;
}

public static void main ( String [ ] args ) { FastReader scan = new FastReader ( ) ; PrintWriter rt = new PrintWriter ( System . out ) ; int y = scan . nextInt ( ) ; String s = scan . next ( ) ; if ( y == 1 ) { rt . print ( " Yes " ) ; rt . close ( ) ; return ; } else { int arr [ ] = new int [ 27 ] ; for ( int i = 0 ; i < s . length ( ) ; i ++ ) { arr [ s . charAt ( i ) - 97 ] ++ ; if ( arr [ s . charAt ( i ) - 97 ] == 2 ) { rt . print ( " YES " ) ; rt . close ( ) ; return ; } } } rt . print ( " NO " ) ; rt . close ( ) ; return ; }
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