A lonely fort was being desperately defended against thousand of attackers.
The attacks came regularly at noon every day, and defending commander knew he had to survive only three more days before his reinforcements arrived.
The attackers are superstitious and believe that multiples of seven are a bad omen. If they see seven or multiple of seven along each side of the fort, they will retreat after firing a few bullets.
With three attacks to come and only 24 defenders , the commander places his defenders as follows: Five along each wall and one in each corner. The attackers saw seven defenders on all sides east¸ west, north and south. They ran back after firing some shots. In that process the commander lost four of his men.
How can he rearrange the remaining 20 so that by noon of next day there will be 7 defenders on each side ?
Some how he did that , but in the second day five men have been killed.
Is it possible for the commander to arrange seven along each wall with only 15 men?
In other words, can they survive that , third and final day of attack?