Why Am I getting MissingMethodException message?

so i inputed a script to turn a flashlight on/off and i check the console and i keep gettin this message
MissingMethodException: Method not found: ‘UnityEngine.Input.getkeydown’.
Boo.Lang.Runtime.DynamicDispatching.MethodDispatcherFactory.ProduceExtensionDispatcher ()
Boo.Lang.Runtime.DynamicDispatching.MethodDispatcherFactory.Create ()
Boo.Lang.Runtime.RuntimeServices.DoCreateMethodDispatcher (System.Object target, System.Type targetType, System.String name, System.Object args)
Boo.Lang.Runtime.RuntimeServices.CreateMethodDispatcher (System.Object target, System.String name, System.Object args)
Boo.Lang.Runtime.RuntimeServices+c__AnonStorey14.<>m__7 ()
Boo.Lang.Runtime.DynamicDispatching.DispatcherCache.Get (Boo.Lang.Runtime.DynamicDispatching.DispatcherKey key, Boo.Lang.Runtime.DynamicDispatching.DispatcherFactory factory)
Boo.Lang.Runtime.RuntimeServices.GetDispatcher (System.Object target, System.String cacheKeyName, System.Type cacheKeyTypes, Boo.Lang.Runtime.DynamicDispatching.DispatcherFactory factory)
Boo.Lang.Runtime.RuntimeServices.GetDispatcher (System.Object target, System.Object args, System.String cacheKeyName, Boo.Lang.Runtime.DynamicDispatching.DispatcherFactory factory)
Boo.Lang.Runtime.RuntimeServices.Invoke (System.Object target, System.String name, System.Object args)
Flashlight.Update () (at Assets/Standard Assets/Projectors/Flashlight.js:3)
and the script is
function Update () {

if (Input.getkeydown("f")) {

    if (light.enabled == true)
        light.enabled = false;
        else
        
        light.enabled = true;
        }

}

aswell as there are 2 listeners in this make sure that tere is only 1 listener and the only thing i have open is skype to talk to my friend cause of the game were devlopin/making
any help would be greatly appreciated thanks

From the documentation

The function is named GetKeyDown, not getKeyDown.

It will be

Input.GetKeyDown(KeyCode.F)

thanks a lot Dave Carlile it shall now work