A program to encrypt and decrypt some text.
psbcd bevo yp psqrd mvel sc...iye ny xyd dkvu klyed psqrd mvel. dro comyxn bevo yp psqrd mvel sc...iye ny xyd dkvu klyed psqrd mvel. sp cywoyxo ckic "cdyz" yb qyoc vswz, dkzc yed, dro psqrd sc yfob. yxvi dgy qeic dy k psqrd. yxo psqrd kd k dswo. xy crsbdc, xy cryoc. psqrdc gsvv qy yx kc vyxq kc droi rkfo dy sp drsc sc iyeb psbcd dswo kd psqrd mvel, iye rkfo dy psqrd.