They will start walk from a single point A in opposite direction .. touching the circumference of the land.. and until they meet at a point B. Once meet, they will create a line touching A nd B , which help to divide the land into 2 parts … each son can take one part…

Y , U
Are in YoU and around YoU … got it ? ?

If you make half each pills , it wont resolve the problem.. still we dont know which one is A and which is B..
Only solution is ..  
Take another from A .. so now you have 2 A and 2 B pills..
Make powder ,  divide into 2 parts…  take  one part each day  for 2 days …