:Input "NUMBER: ",A
:If A<2 or fPart(A
:Then
:Disp "INVALID INPUT"
:Stop
:End
:0->B
:2->I
:While I<A and not(B
:If 0=fPart(A/I
:1->B
:I+2->I
:If I=4
:3->I
:End
:If B
:Disp "NOT"
:Disp "PRIME"