Calculate the average male median age of all the residential areas in Windham county.
average male median age refers to Divide (Sum(male_median_age), Count(county)); 'WINDHAM' is the county
SELECT SUM(T2.male_median_age) / COUNT(T2.median_age) FROM country AS T1 INNER JOIN zip_data AS T2 ON T1.zip_code = T2.zip_code WHERE T1.county = 'WINDHAM'