local player = game:GetService("Players").LocalPlayer
local uis = game:GetService("UserInputService")
local keyCode = Enum.Keycode.LeftShift
local runDiff = -7

uis.InputBegan:Connect(function(input, gameProcessed)
    if not gameProcessed and player.Character:FindFirstChild("Humanoid") then
        if input == keyCode then
            player.Character.Humanoid.Walkspeed += runDiff
        end
    end
end

uis.InputEnded:Connect(function(input, gameProcessed)
    if not gameProcessed and player.Character:FindFirstChild("Humanoid") then
        if input == keyCode then
            player.Character.Humanoid.Walkspeed -= runDiff
        end
    end
end