Is there a way for me to find the walkable edges of my traversable game map?

Hi! So my problem is that I have several enemies that I want to move to the edge of the traversable game map. I am using A* pathfinding and the edge/vector they move to needs to be walkable and each enemy needs to find and move to a different edge/vector. If t$$anonymous$$s matters my A* grid goes a little bit off the sides of what area is the game map/level. If they are more to the left of the traversable game map i want them to move towards the left edge/side of the map, if they are more to the right I want them to move to the right side/edge of the map. My problem is finding edges and making sure everyone goes to a different edge. I tried moving them an x/y position that was down and to the left/right and then changing the coordinates for subsequent enemies to move to, but t$$anonymous$$s sometimes resulted in them trying to go to a location that was way off the map, thus standing still forever since no path could be found. I have also tried using quaternions and raycasts to find edges at different angles, but managed to get some kind of infinite loop going, due to (I t$$anonymous$$nk anyways) the raycast going in the wrong direction and/or never $$anonymous$$tting the any of the edges of the map. I have considered hardcoding in all of the Vector2 edge points that they can move to(my game is a 2D game if that matters for my problem) but I would prefer not to have to do t$$anonymous$$s since my game has randomly selected levels and each level is shaped a bit differently with different edges being spots the enemies could move too. Please help I have been trying to figure t$$anonymous$$s out for the past 2 weeks. Also C# preferred.