Nan Nan Nan error in standard assets mouse look script

i am making a fps game i added the standard assets FPS controller to my scene.Suddenly it says in console that inputRotation is not valid(Nan,Nan,Nan,1.000000)i am using the standard assets fps and mouse look script please help me.its my first game i dont want it to get ruined please help me

Nan stands for not a number, can you look into where the rotation is coming from? Perhaps post the script? Have you made any modifications to the script or fps controller prefab, was it working before? What version of unity are you on?