how do i run a function when a character is added to the world?

i need to define the players character as a variable and i need to wait until its added its giving me index nil "CharacterAdded" for the line that should run the code

local function GetDistance(p1,p2)
	local Distance = (p1.Position - p2.Position).magnitude
	return Distance
end
players = game:GetService("Players")
local function start()
	local character = players.LocalPlayer.Character.PrimaryPart
	local button = script.Parent
	while wait(0.1) do 
		if GetDistance(button - character) > 10 then
			print("E")
		end
	end
end


game.Players.PlayerAdded:Connect(function()	
	game.Players.LocalPlayer.CharacterAdded:Connect(start)
end)

inside the PlayerAdded event you need to pass the player joining as a parameter so game.Players.PlayerAdded:Connect(function(player) player.CharacterAdded:Connect(start) end) this should work