Will this script even work, and whats the problem with it?

I tried to make a running script ,but when i tried to test it it says "attempt to index local 'Player' (a nil value) on the line 2".

local Player = game.Players.LocalPlayer
local Character = Player.Character
local Human = game.Players.LocalPlayer.Character

game:GetService("UserInputService").InputBegan:connect(function(input, gameprocesed)
    if input.KeyDown == Enum.KeyCode.LeftShift then
       for i = 1,16 do 
            Human:WaitForChild("Humanoid").WalkSpeed = 30
        end
    end
end)

game:GetService("UserInputService").Input.Ended:connect(function(input, gameprocesed)
    if input.KeyDown == Enum.KeyCode.LeftShift then
        for i = 1,16 do
            Human:WaitForChild("Humanoid").WalkSpeed = 16
        end
    end
end)