You are standing on a historic site. On your right site the Kanonenmätteli, on your left the fountain with Adrian von Bubenberg and in front of you the town which he defended succesfully in 1476 when Charles the Bold, the duke of Burgundy attacked the city. "As long as a vene lives in us, no one gives up!" he shouted to his soldiers. Take you back in this time. 

In front of the gate is a guard: Who wants in the city, has to know the correct password. Next to you at the fountain is a traveler who soaks his horse. Togehter you observe the events:

A first farmer comes to the guard. The guard says: "16" and the farmer answers: "7". He is admitted.

Shortly a market trader comes and the guard shouts "8". The woman slows down and says "5". She can get in as well. 

A friar comes to the gate and asks for entrance. "28" says the guard. The friar thinks, lets his rosary slip through his fingers and answers deliberatly: "11". The guard opens the gate again.

The traveler laughs and says to you: That is so easy! He takes his horse and goes to the gate. "12" says the guard, "6" replies the traveler. The guard sounds alarm immediatly, the traveler is put in chains and discharged.