vasul de 7 l | vasul de 3 l
_________ |___________
0 litri | 3 litri
_________ |___________
3 litri | 0 litri
_________ |___________
3 litri | 3 litri
_________|___________
6 litri | 0 litri
_________ |___________
6 litri | 3 litri
________ |___________
7 litri | 2 litri
_________|____________