You've got two jars, one of them fits exactly 5 litres, the other one fits exactly 3 litres. How could you get exactly 4 litres with these two jars? It is allowed to spoil some water.

Mr. House would like to visit his old friend Mr. Street, who is living in the main street of a small village. The main steet has 50 houses divided into two blocks and numbered from 1 to 20 and 21 to 50. Since Mr. House has forgotten the number, he asks it from a passer-by, who replies "Just try to guess it." Mr. House likes playing games and asks three questions:

1. In which block is it?
2. Is the number even?
3. Is it a square?

After Mr. House has received the answers, he says: "I'm still doubting, but if you'll tell me whether the digit 4 is in the number, I will know the answer!". Then Mr. House runs to the building in which he thinks his friend is living. He rings, a man opens the door and it turns out that he's wrong. The man starts laughing and tells Mr. House: "Your advisor is the biggest liar of the whole village. He never speaks the truth!". Mr. House thinks for a moment and says "Thanks, now I know the real address of Mr. Street".
What is the adress of Mr. Street?

What belongs to you but others use it more than you do?