question: How many days after the Bulgarians entered Prokuplje did the Hungarians enter Kursumlija?
#1 return Bulgarians entered Prokuplje 
#2 return Hungarians did enter Kursumlija 
#3 return when  was  #1 
#4 return when  was  #2 
#5 return difference of #3 and  #4 in  days