Problems from:
- spoj-br: http://br.spoj.com/
- spoj-pl-: http://pl.spoj.com/
- live-archive: https://icpcarchive.ecs.baylor.edu/
- uva: http://uva.onlinejudge.org/
- codeforces: http://codeforces.com/
- coj: http://coj.uci.cu/
- poj: http://poj.org/
- eolimp: http://www.e-olimp.com/
- google-code-jam: https://code.google.com/codejam/
- kattis: https://icpc.kattis.com/
- seletiva-imeusp: http://www.ime.usp.br/~cef/maratona.html
- topcoder: http://community.topcoder.com/tc
- yandex: http://algorithm.contest.yandex.com/
- uri: http://www.urionlinejudge.com.br/judge/