EC $1.$ In a prison, there is a door b$/$w any pair of adjacent cells and one exit guarded by a guard G$.$ One prisoner is a maniac M which kills anybody he can see when he enters a cell. If M returns to the cell with his victim, then he loses consciousness and stops. In the evening all inmates and the guard went to sleep in their cells. In the morning, maniac M is gone and all other prisoners with the guard were found dead in their cells. Show the route of the maniac.

EC$2$ Give an algorithm that exchanges $2$ memory units without extra memory

HW $1$ Given $5$ rocks of different weight and lever scales, in $7$ tests sort the rocks by weight.

Describe the method that finds the correct order by the $7$th comparison.