How many days after Riga was captured by the Red Army was the Latvian Socialist Soviet Republic officially proclaimed?
return Riga was  captured by the  Red Army ;return the  Latvian Socialist Soviet Republic was  officially proclaimed ;return when  was  #1 ;return when  was  #2 ;return difference of #4 and  #3 in  days
['select', 'select', 'project', 'project', 'arithmetic']