deveres de casa:

http://br.spoj.pl/problems/PAR/
http://br.spoj.pl/problems/BAFO/
http://br.spoj.pl/problems/OBITETRI/
http://br.spoj.pl/problems/QUERM/
http://br.spoj.pl/problems/TV/
http://br.spoj.pl/problems/ENERGIA/
http://acmicpc-live-archive.uva.es/nuevoportal/data/problem.php?p=2043
http://acmicpc-live-archive.uva.es/nuevoportal/data/problem.php?p=3527
http://acmicpc-live-archive.uva.es/nuevoportal/data/problem.php?p=3045 
http://uva.onlinejudge.org/external/114/11455.html
http://acmicpc-live-archive.uva.es/nuevoportal/data/problem.php?p=3543
http://acmicpc-live-archive.uva.es/nuevoportal/data/problem.php?p=3544

http://acmicpc-live-archive.uva.es/nuevoportal/data/problem.php?p=2432
http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=212&page=show_problem&problem=120
http://acmicpc-live-archive.uva.es/nuevoportal/data/problem.php?p=3639
http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=214&page=show_problem&problem=2432
http://br.spoj.pl/problems/SALDO/
http://br.spoj.pl/problems/MACACO/
http://br.spoj.pl/problems/REDOTICA/
http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&category=12&problem=978
http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=13&page=show_problem&problem=1109

http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=80&page=show_problem&problem=2498
http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=189&page=show_problem&problem=2383
http://acmicpc-live-archive.uva.es/nuevoportal/data/problem.php?p=3197
http://acmicpc-live-archive.uva.es/nuevoportal/data/problem.php?p=4056
http://br.spoj.pl/problems/BABEL/
http://br.spoj.pl/problems/SORVETE/
http://acmicpc-live-archive.uva.es/nuevoportal/data/problem.php?p=2824
http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=79&page=show_problem&problem=2521

http://codeforces.com/contest/31/problem/D
http://uva.onlinejudge.org/index.php?option=onlinejudge&page=show_problem&problem=1297
https://www.spoj.pl/problems/PERMUT1/
http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=217&page=show_problem&problem=419
http://acmicpc-live-archive.uva.es/nuevoportal/data/problem.php?p=4403
https://www.spoj.pl/problems/MARBLES/
http://br.spoj.pl/problems/DESCULPA/
http://br.spoj.pl/problems/DOMINO/

contests:

http://codeforces.com/contest/34/problem/A
http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=12&page=show_problem&problem=944
http://acmicpc-live-archive.uva.es/nuevoportal/data/problem.php?p=3912
http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=193&page=show_problem&problem=1391
http://uva.onlinejudge.org/index.php?option=onlinejudge&page=show_problem&problem=1318
http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=188&page=show_problem&problem=484
http://acmicpc-live-archive.uva.es/nuevoportal/data/problem.php?p=2158

http://codeforces.com/contest/34/problem/B
https://www.spoj.pl/problems/AGGRCOW/
http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=162&page=show_problem&problem=2172
http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=12&page=show_problem&problem=990
http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=188&page=show_problem&problem=2461
http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=196&page=show_problem&problem=932
https://www.spoj.pl/problems/CFPARTY

http://acm.sgu.ru/problem.php?contest=0&problem=196
http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&page=show_problem&category=22&problem=2010
http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=26&page=show_problem&problem=2408
http://acmicpc-live-archive.uva.es/nuevoportal/data/problem.php?p=4104
http://acm.sgu.ru/problem.php?contest=0&problem=495
http://acmicpc-live-archive.uva.es/nuevoportal/data/problem.php?p=3375
https://www.spoj.pl/problems/PT07Y/
http://uva.onlinejudge.org/index.php?option=com_onlinejudge&Itemid=8&category=154&page=show_problem&problem=945