For how many years after the Goryeo-Mongol assault first began did the Mongols directly control Tamna?
return Goryeo-Mongol assault first began ;return when  was  #1 ;return the  Mongols directly control Tamna ;return when  was  #3 ;return difference of #4 and  #2 in  years
['select', 'project', 'select', 'project', 'arithmetic']