public static void main ( String [ ] args ) throws IOException {
  BufferedReader br = new BufferedReader ( new InputStreamReader ( System . in ) ) ;
  String str = br . readLine ( ) ;
  String [ ] ABK = str . split ( " " ) ;
  int cont = 0 ;
  for ( int i = Math . min ( Integer . parseInt ( ABK [ 0 ] ) , Integer . parseInt ( ABK [ 1 ] ) ) ;
  i > 0 ;
  i -- ) {
    if ( Integer . parseInt ( ABK [ 0 ] ) % i == 0 && Integer . parseInt ( ABK [ 1 ] ) % i == 0 ) {
      cont ++ ;
      if ( cont == Integer . parseInt ( ABK [ 2 ] ) ) {
        System . out . println ( i ) ;
        return ;
      }
    }
  }
}

public static void main ( String [ ] args ) throws IOException { BufferedReader br = new BufferedReader ( new InputStreamReader ( System . in ) ) ; String str = br . readLine ( ) ; String [ ] ABK = str . split ( " ▁ " ) ; int cont = 0 ; for ( int i = Math . min ( Integer . parseInt ( ABK [ 0 ] ) , Integer . parseInt ( ABK [ 1 ] ) ) ; i > 0 ; i -- ) { if ( Integer . parseInt ( ABK [ 0 ] ) % i == 0 && Integer . parseInt ( ABK [ 1 ] ) % i == 0 ) { cont ++ ; if ( cont == Integer . parseInt ( ABK [ 2 ] ) ) { System . out . println ( i ) ; return ; } } } }
(method_declaration (modifiers) type: (void_type) name: (identifier) parameters: (formal_parameters (formal_parameter type: (array_type element: (type_identifier) dimensions: (dimensions)) name: (identifier))) (throws (type_identifier)) body: (block (local_variable_declaration type: (type_identifier) declarator: (variable_declarator name: (identifier) value: (object_creation_expression type: (type_identifier) arguments: (argument_list (object_creation_expression type: (type_identifier) arguments: (argument_list (field_access object: (identifier) field: (identifier)))))))) (local_variable_declaration type: (type_identifier) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list)))) (local_variable_declaration type: (array_type element: (type_identifier) dimensions: (dimensions)) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (string_literal))))) (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (decimal_integer_literal))) (for_statement init: (local_variable_declaration type: (integral_type) declarator: (variable_declarator name: (identifier) value: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (array_access array: (identifier) index: (decimal_integer_literal)))) (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (array_access array: (identifier) index: (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: (binary_expression left: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (array_access array: (identifier) index: (decimal_integer_literal)))) right: (identifier)) right: (decimal_integer_literal)) right: (binary_expression left: (binary_expression left: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (array_access array: (identifier) index: (decimal_integer_literal)))) right: (identifier)) right: (decimal_integer_literal)))) consequence: (block (expression_statement (update_expression (identifier))) (if_statement condition: (parenthesized_expression (binary_expression left: (identifier) right: (method_invocation object: (identifier) name: (identifier) arguments: (argument_list (array_access array: (identifier) index: (decimal_integer_literal)))))) consequence: (block (expression_statement (method_invocation object: (field_access object: (identifier) field: (identifier)) name: (identifier) arguments: (argument_list (identifier)))) (return_statement)))))))))