End the game when only one sprite is left.

Hi, i have a 4 player game and i want to have it so when one sprite is left they win but i dont know how. anyone know?

4 players.
When a player dies, have it send a message to the other 3.
Players have a mailbox (the green triangle in this drawing, probably should have been red, oh well), 3 mailboxes from p1 p2 p3 or p4 that turn on on/off switches. The always (at the top) will go through all 3 gates when they are on, and goes to the Next level behavior.
Repeat for all players so they get 3 messages from the other players when they die.