Among students with 1 month of absenses, how many of them are enlisted in the air force department?
1 month of absences refers to month = 1; department refers to organ; organ = 'air_force';
SELECT COUNT(T1.name) FROM longest_absense_from_school AS T1 INNER JOIN enlist AS T2 ON T1.name = T2.name WHERE T1.month = 1 AND T2.organ = 'air_force'