A system comprising: a plurality of authentication servers (213, 223), each authentication server being provided in a different region (210, 220); an integrated entrance server for providing a login page; and a client arranged to provide a web browser for a user to access the login page from the integrated entrance server and input user information, wherein the integrated entrance server includes identification means for identifying a region to which a user belongs based on receiving the inputted user information from the web browser, and transmission means for transmitting the identified region identified by the identification means to the web browser, wherein the client includes access means for (i) accessing one of the plurality of authentication servers based on the identified region transmitted by the transmission means, and (ii) providing the user information to the accessed authentication server, wherein the accessed authentication server includes authentication means for authenticating the user based on the received user information, and setting means for setting cookie information on the web browser in response to the user being authenticated by the authentication means, wherein the cookie information is set to comprise (i) an authentication token indicating that the user has logged in and (ii) identification information indicating that the user has logged in via the integrated entrance server, and wherein, in a case where the system performs re-authentication of a user, the accessed authentication server is configured to check, on a basis of the cookie information on the web browser, whether the user previously logged in via the integrated entrance server or via the accessed authentication server without using the integrated entrance server, respond with a redirect response to the login page of the integrated entrance server after invalidating the cookie information in a case where the user has logged in via the integrated entrance server, and respond with a login page of the accessed authentication server after invalidating the cookie information in a case where the user has logged in via the accessed authentication server without using the integrated entrance server. a plurality of authentication servers (213, 223), each authentication server being provided in a different region (210, 220); an integrated entrance server for providing a login page; and a client arranged to provide a web browser for a user to access the login page from the integrated entrance server and input user information, wherein the integrated entrance server includes identification means for identifying a region to which a user belongs based on receiving the inputted user information from the web browser, and transmission means for transmitting the identified region identified by the identification means to the web browser, wherein the client includes access means for (i) accessing one of the plurality of authentication servers based on the identified region transmitted by the transmission means, and (ii) providing the user information to the accessed authentication server, wherein the accessed authentication server includes authentication means for authenticating the user based on the received user information, and setting means for setting cookie information on the web browser in response to the user being authenticated by the authentication means, wherein the cookie information is set to comprise (i) an authentication token indicating that the user has logged in and (ii) identification information indicating that the user has logged in via the integrated entrance server, and wherein, in a case where the system performs re-authentication of a user, the accessed authentication server is configured to check, on a basis of the cookie information on the web browser, whether the user previously logged in via the integrated entrance server or via the accessed authentication server without using the integrated entrance server, respond with a redirect response to the login page of the integrated entrance server after invalidating the cookie information in a case where the user has logged in via the integrated entrance server, and respond with a login page of the accessed authentication server after invalidating the cookie information in a case where the user has logged in via the accessed authentication server without using the integrated entrance server.