public static void main ( String [ ] args ) throws IOException {
  StringTokenizer st ;
  BufferedReader f = new BufferedReader ( new InputStreamReader ( System . in ) ) ;
  st = new StringTokenizer ( f . readLine ( ) ) ;
  String curr = st . nextToken ( ) ;
  int op = 0 ;
  int n = curr . length ( ) ;
  int [ ] psums = new int [ n + 1 ] ;
  int [ ] psums1 = new int [ n + 1 ] ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) {
    if ( curr . charAt ( i ) == 'a' ) {
      psums [ i + 1 ] = psums [ i ] + 1 ;
      psums1 [ i + 1 ] = psums1 [ i ] ;
    }
    else {
      psums1 [ i + 1 ] = psums1 [ i ] + 1 ;
      psums [ i + 1 ] = psums [ i ] ;
    }
  }
  f . close ( ) ;
  for ( int i = 0 ;
  i < n + 1 ;
  i ++ ) {
    for ( int x = i ;
    x < n + 1 ;
    x ++ ) {
      int p1 = psums [ i ] ;
      int p2 = psums1 [ x ] - psums1 [ i ] ;
      int p3 = psums [ n ] - psums [ x ] ;
      op = Math . max ( p1 + p2 + p3 , op ) ;
    }
  }
  System . out . println ( op ) ;
}

public static void main ( String [ ] args ) throws IOException { StringTokenizer st ; BufferedReader f = new BufferedReader ( new InputStreamReader ( System . in ) ) ; st = new StringTokenizer ( f . readLine ( ) ) ; String curr = st . nextToken ( ) ; int op = 0 ; int n = curr . length ( ) ; int [ ] psums = new int [ n + 1 ] ; int [ ] psums1 = new int [ n + 1 ] ; for ( int i = 0 ; i < n ; i ++ ) { if ( curr . charAt ( i ) == ' a ' ) { psums [ i + 1 ] = psums [ i ] + 1 ; psums1 [ i + 1 ] = psums1 [ i ] ; } else { psums1 [ i + 1 ] = psums1 [ i ] + 1 ; psums [ i + 1 ] = psums [ i ] ; } } f . close ( ) ; for ( int i = 0 ; i < n + 1 ; i ++ ) { for ( int x = i ; x < n + 1 ; x ++ ) { int p1 = psums [ i ] ; int p2 = psums1 [ x ] - psums1 [ i ] ; int p3 = psums [ n ] - psums [ x ] ; op = Math . max ( p1 + p2 + p3 , op ) ; } } System . out . println ( op ) ; }
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