Scientific Reports 7: Article number: 46237; published online: 10 April 2017; updated: 04 May 2017

In the original version of this Article, Yusen Zhang was incorrectly affiliated with ‘Faculty of Science, University of Kragujevac, P. O. Box 60, 34000 Kragujevac, Serbia’. The correct affiliation is listed below.

School of Mathematics and Statistics, Shandong University at Weihai, Weihai 264209, China.

This error has now been corrected in the PDF and HTML versions of the Article.