Among the coaches who have taught the Philadelphia Flyers, how many of them are born in March?
born in March refers to birthMon = 3; Philadelphia Flyers is the name of team;
SELECT COUNT(DISTINCT T3.coachID) FROM Coaches AS T1 INNER JOIN Teams AS T2 ON T1.year = T2.year AND T1.tmID = T2.tmID INNER JOIN Master AS T3 ON T1.coachID = T3.coachID WHERE T2.name = 'Philadelphia Flyers' AND T3.birthMon = 3