How many tourists that visited from January to June of 2008 and 2009 combined were foreign?
return foreign tourists ;return #1 that visited from  January to June in  2008 ;return #1 that visited from  January to June in  2009 ;return number of  #2 ;return number of  #3 ;return sum of #4 and  #5
['select', 'filter', 'filter', 'aggregate', 'aggregate', 'arithmetic']