Updated list of problem sets

problem-sets-competitive-programming.md

@@ -18,6 +18,7 @@
 * [Internet Problem Solving Contest](http://ipsc.ksp.sk/)
 * [Just another Golf Coding](http://jagc.org/)
 * [Microcorruption](https://microcorruption.com/)
+* [Saratov State University](http://acm.sgu.ru/index.php)
 * [Topcoder](https://www.topcoder.com/)
 
 
@@ -27,10 +28,12 @@
 * [Caribbean Online Judge](http://coj.uci.cu/24h/problems.xhtm)
 * [CheckIO](http://www.checkio.org/)
 * [CodeHunt](https://www.codehunt.com/)
+* [Codibility](https://codility.com/programmers/)
 * [Coding Bat](http://codingbat.com/java)
 * [Exercism](http://exercism.io/)
 * [Google Code Jam - Practise](https://code.google.com/codejam/contests.html)
 * [Hacker.org](http://www.hacker.org/)
+* [HackerEarth](https://www.hackerearth.com/)
 * [Leetcode](https://leetcode.com/)
 * [Mathproblem of the Month - Bilkent University](http://www.fen.bilkent.edu.tr/~cvmath/prob-month.html)
 * [PEG Judge](http://wcipeg.com/)