public static void main ( String [ ] args ) {
  Scanner in = new Scanner ( System . in ) ;
  String s = in . next ( ) ;
  int c = 0 , i ;
  in . close ( ) ;
  for ( i = 0 ;
  i < s . length ( ) ;
  i ++ ) {
    if ( i < s . length ( ) - 2 && s . substring ( i , i + 3 ) . equals ( "Ann" ) ) c ++ ;
    if ( i < s . length ( ) - 3 && s . substring ( i , i + 4 ) . equals ( "Olya" ) ) c ++ ;
    if ( i < s . length ( ) - 4 && s . substring ( i , i + 5 ) . equals ( "Danil" ) ) c ++ ;
    if ( i < s . length ( ) - 4 && s . substring ( i , i + 5 ) . equals ( "Slava" ) ) c ++ ;
    if ( i < s . length ( ) - 5 && s . substring ( i , i + 6 ) . equals ( "Nikita" ) ) c ++ ;
  }
  System . out . println ( c == 1 ? "YES" : "NO" ) ;
}

public static void main ( String [ ] args ) { Scanner in = new Scanner ( System . in ) ; String s = in . next ( ) ; int c = 0 , i ; in . close ( ) ; for ( i = 0 ; i < s . length ( ) ; i ++ ) { if ( i < s . length ( ) - 2 && s . substring ( i , i + 3 ) . equals ( " Ann " ) ) c ++ ; if ( i < s . length ( ) - 3 && s . substring ( i , i + 4 ) . equals ( " Olya " ) ) c ++ ; if ( i < s . length ( ) - 4 && s . substring ( i , i + 5 ) . equals ( " Danil " ) ) c ++ ; if ( i < s . length ( ) - 4 && s . substring ( i , i + 5 ) . equals ( " Slava " ) ) c ++ ; if ( i < s . length ( ) - 5 && s . substring ( i , i + 6 ) . equals ( " Nikita " ) ) c ++ ; } System . out . println ( c == 1 ? " YES " : " NO " ) ; }
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