I really really need help

I recently tried to play a game on my PC and apparently had the resolution set too high, and it made my monitor cut to saying input not supported. I tried to cut the computer off and back on but it diddnt work now i cant even sign in, it says input not supported right after boot up. I have windows 10 and i cant get to the safe mode at boot to change the resolution back can someone PLEASE help me?1 i have an alienware R51. Im really really stressed right now and want to scream