Logout of Social Networks from iOS application

In my app i am using google, face book login .I was able to login properly but when i try to logout from google , face book i am using following code.But my problem is even if i logout from my app When i click on login buttons it is asking permissions not login screen.Even if i logout from my app, Do i need to logout in safari browser (clear cookies in settings) or device social apps.

What to do to complete logout from app it self.

[[GPPSignIn sharedInstance] signOut];

//facebook

FBSession* session = [FBSession activeSession];

[session closeAndClearTokenInformation];

[session close];

[FBSession setActiveSession:nil];

NSHTTPCookieStorage* cookies = [NSHTTPCookieStorage sharedHTTPCookieStorage];

NSArray* facebookCookies = [cookies cookiesForURL:[NSURL URLWithString:@"https://facebook.com/"]];

for (NSHTTPCookie* cookie in facebookCookies) {

[cookies deleteCookie:cookie];

}