How many people in total died from smallpox from both Mexico City and Puebla?
return Mexico City ;return Puebla ;return people that died from  smallpox of #1 ;return people that died from  smallpox of #2 ;return number of  #3 ;return number of  #4 ;return sum of #5 and  #6
['select', 'select', 'project', 'project', 'aggregate', 'aggregate', 'arithmetic']