Why won't this command work?

When I put /execute if entity @ a[x=600,y=4,z=-96] run say yes in a repeating command block, it constantly just says yes whether or not there is a player at 600, 4, -96. How can I make it run the command only when any player is at those specific coordinates?

Edit: There is a space in between @ and "a" because without it it would just show a user with the name a