How do i make sure the NPC hunts down the closest Humanoid?

My current script lets the NPC hunt the player who joined last, the NPC doesnt change target until that person leaves. I need to script it so that the NPC hunts the player who is closest, i tried to work it out myself with IntValues. Please someone help me!

function getHumanoid(model)
	for _, v in pairs(model:GetChildren()) do
		if v:IsA'Humanoid' then
			return v
		end
	end
end


local ai = script.Parent
local human = getHumanoid(ai)
local hroot = ai.HumanoidRootPart
local zspeed = hroot.Velocity.magnitude


local pfs = game:GetService("PathfindingService")

function GetPlayerNames()
	local players = game:GetService('Players'):GetChildren()
	local name = nil
	for _, v in pairs(players) do
		if v:IsA'Player' then
			name = tostring(v.Name)
		end
	end
	return name
end

spawn(function()
	while wait() do
		print()
	end
end)

function GetPlayersBodyParts(t)
	local torso = t
	if torso then
		local figure = torso.Parent
		for _, v in pairs(figure:GetChildren()) do
			if v:IsA'Part' then
				return v.Name
			end
		end
	else
		return "HumanoidRootPart"
	end
end

function GetTorso(part)
	local chars = game.Workspace:GetChildren()
	local torso = nil
	for _, v in pairs(chars) do
		if v:IsA'Model' and v ~= script.Parent and v.Name == GetPlayerNames() then
			local charRoot = v:FindFirstChild'HumanoidRootPart'
			if (charRoot.Position - part).magnitude < SearchDistance then
				torso = charRoot
			end
		end
	end
	return torso
end