flickr not able to parse JSON

I am using flickr public API, Where I am facing issue with parsing of JSON. Here is my code.

 NSString *urlString = @"https://api.flickr.com/services/feeds/photos_public.gne?format=json";
    NSURL *url = [NSURL URLWithString:urlString];
    NSURLRequest *request = [NSURLRequest requestWithURL:url];

    AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
   // operation.responseSerializer = [AFJSONResponseSerializer serializer];

    [operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {

        //(JSON text did not start with array or object and option to allow fragments not set.)
        NSString *rawString = [[NSString alloc] initWithData:responseObject encoding:NSUTF8StringEncoding];

        NSData *refinedData = [responseObject subdataWithRange:NSMakeRange([@"jsonFlickrFeed(" length], [responseObject length]-([@"jsonFlickrFeed(" length]+1))];
        NSError *parseError = nil;

        NSDictionary *jsonObject=[NSJSONSerialization
                                  JSONObjectWithData:refinedData
                                  options:NSJSONReadingMutableLeaves
                                  error:&parseError];
        NSError *parsingError = nil;



    } failure:^(AFHTTPRequestOperation *operation, NSError *error) {


    }];

    [operation start];

Error while parsing:

Error Domain=NSCocoaErrorDomain Code=3840 "The data couldn’t be read because it isn’t in the correct format." (Invalid escape sequence around character 15901.) UserInfo=0x7fa613da71c0 {NSDebugDescription=Invalid escape sequence around character 15901.}

Is there any specific character set should i need to specify while parsing?

What ever the changes required that needs to be done at my end since the API response is not in my control.

Solution: @vishnuvaran's guess logically correct, Apart from that we need to escape "\'" this character then only I can able to parse the JSON.

[requiredString replaceOccurrencesOfString:@"\\\'"  withString:@" "   options:NSLiteralSearch range:NSMakeRange(0, [requiredString length])];

You are giving wrong sub data range.Just change this line

NSData *refinedData = [responseObject subdataWithRange:NSMakeRange([@"jsonFlickrFeed(" length], [responseObject length]-([@"jsonFlickrFeed(" length]+1))];

to below line

NSData *refinedData = [responseObject subdataWithRange:NSMakeRange([@"jsonFlickrFeed(" length], ([responseObject length]-1)-([@"jsonFlickrFeed(" length]))];

Hope it will help you.