public static void main ( String [ ] args ) {
  Scanner sc = new Scanner ( System . in ) ;
  String str1 = sc . nextLine ( ) ;
  String str2 = sc . nextLine ( ) ;
  char [ ] arr1 = str1 . toCharArray ( ) ;
  char [ ] arr2 = str2 . toCharArray ( ) ;
  int [ ] map1 = new int [ 26 ] ;
  Arrays . fill ( map1 , 0 ) ;
  int [ ] map2 = new int [ 26 ] ;
  Arrays . fill ( map2 , 0 ) ;
  int count = 0 ;
  for ( int i = 0 ;
  i < str1 . length ( ) ;
  i ++ ) {
    map1 [ arr1 [ i ] - 'a' ] ++ ;
  }
  for ( int i = 0 ;
  i < str2 . length ( ) ;
  i ++ ) {
    map2 [ arr2 [ i ] - 'a' ] ++ ;
  }
  for ( int i = 0 ;
  i < 26 ;
  i ++ ) {
    if ( map2 [ i ] > 0 ) {
      if ( map1 [ i ] == 0 ) {
        count = - 1 ;
        break ;
      }
      else if ( map1 [ i ] >= map2 [ i ] ) {
        count += map2 [ i ] ;
      }
      else {
        count += map1 [ i ] ;
      }
    }
  }
  if ( count == 0 ) {
    count = - 1 ;
  }
  System . out . println ( count ) ;
}

public static void main ( String [ ] args ) { Scanner sc = new Scanner ( System . in ) ; String str1 = sc . nextLine ( ) ; String str2 = sc . nextLine ( ) ; char [ ] arr1 = str1 . toCharArray ( ) ; char [ ] arr2 = str2 . toCharArray ( ) ; int [ ] map1 = new int [ 26 ] ; Arrays . fill ( map1 , 0 ) ; int [ ] map2 = new int [ 26 ] ; Arrays . fill ( map2 , 0 ) ; int count = 0 ; for ( int i = 0 ; i < str1 . length ( ) ; i ++ ) { map1 [ arr1 [ i ] - ' a ' ] ++ ; } for ( int i = 0 ; i < str2 . length ( ) ; i ++ ) { map2 [ arr2 [ i ] - ' a ' ] ++ ; } for ( int i = 0 ; i < 26 ; i ++ ) { if ( map2 [ i ] > 0 ) { if ( map1 [ i ] == 0 ) { count = - 1 ; break ; } else if ( map1 [ i ] >= map2 [ i ] ) { count += map2 [ i ] ; } else { count += map1 [ i ] ; } } } if ( count == 0 ) { count = - 1 ; } System . out . println ( count ) ; }
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