How many months passed between the Ottoman force defeated 4,000 Serbs at Demotika and the first unsuccessful attempt to seize Constantinople was made by John V?
return the  Ottoman force defeated 4,000 Serbs at Demotika ;return the  first unsuccessful attempt to seize Constantinople made by John V ;return month of #1 ;return month of #2 ;return the  difference of #4 and  #3
['select', 'select', 'project', 'project', 'arithmetic']