static String K_String ( String s , int k ) {
  int n = s . length ( ) ;
  int fre [ ] = new int [ 26 ] ;
  for ( int i = 0 ;
  i < n ;
  i ++ ) fre [ s . charAt ( i ) - 'a' ] ++ ;
  String str = "" ;
  for ( int i = 0 ;
  i < 26 ;
  i ++ ) {
    if ( fre [ i ] % k == 0 ) {
      int x = fre [ i ] / k ;
      while ( x != 0 ) {
        str += ( char ) ( i + 'a' ) ;
        x -- ;
      }
    }
    else {
      return "-1" ;
    }
  }
  return str ;
}

static String K_String ( String s , int k ) { int n = s . length ( ) ; int fre [ ] = new int [ 26 ] ; for ( int i = 0 ; i < n ; i ++ ) fre [ s . charAt ( i ) - ' a ' ] ++ ; String str = " " ; for ( int i = 0 ; i < 26 ; i ++ ) { if ( fre [ i ] % k == 0 ) { int x = fre [ i ] / k ; while ( x != 0 ) { str += ( char ) ( i + ' a ' ) ; x -- ; } } else { return " - 1" ; } } return str ; }
(method_declaration (modifiers) type: (type_identifier) name: (identifier) parameters: (formal_parameters (formal_parameter type: (type_identifier) name: (identifier)) (formal_parameter type: (integral_type) name: (identifier))) body: (block (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) dimensions: (dimensions) value: (array_creation_expression type: (integral_type) dimensions: (dimensions_expr (decimal_integer_literal))))) (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (identifier) right: (identifier)) update: (update_expression (identifier)) body: (expression_statement (update_expression (array_access array: (identifier) index: (binary_expression left: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (identifier))) right: (character_literal)))))) (local_variable_declaration type: (type_identifier) declarator: (variable_declarator name: (identifier) value: (string_literal))) (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) condition: (binary_expression left: (identifier) right: (decimal_integer_literal)) update: (update_expression (identifier)) body: (block (if_statement condition: (parenthesized_expression (binary_expression left: (binary_expression left: (array_access array: (identifier) index: (identifier)) right: (identifier)) right: (decimal_integer_literal))) consequence: (block (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (binary_expression left: (array_access array: (identifier) index: (identifier)) right: (identifier)))) (while_statement condition: (parenthesized_expression (binary_expression left: (identifier) right: (decimal_integer_literal))) body: (block (expression_statement (assignment_expression left: (identifier) right: (cast_expression type: (integral_type) value: (parenthesized_expression (binary_expression left: (identifier) right: (character_literal)))))) (expression_statement (update_expression (identifier)))))) alternative: (block (return_statement (string_literal)))))) (return_statement (identifier))))