My keyboard doesn't type certain letters

My keyboard is not typing certain letters. It is not typing the letters b, c, m, n, v, x, and y. The computer is locked and my password contains some of these letters. The keyboard is plugged in, the keys were not stuck, and I can't get into the computer to try to fix it. I don't want to make any purchases, I would prefer not to. Please tell me what to do.