Get post_id after posting an image on facebook using graph api in ios?

I am using Facebook graph API to post image on Facebook, image is posted successfully by using this call

[FBRequestConnection startForUploadPhoto:[UIImage imageNamed:@"selfie"] completionHandler:^(FBRequestConnection *connection, id result, NSError *error) {
        if (!error) {
            // Status update posted successfully to Facebook
            NSLog(@"result: %@", result);
        } else {
            NSLog(@"%@", error.description);
        }
    }];

but in response I get the same post_id for every post that I make but different id

{
    id = 1603950186487123;
    "post_id" = "1600090656873076_1603941126488029";
}

I want to fetch likes on a particular post using post_id using this graph API but this give me blank response every time.Now the question is why the post_id is same every time?