input issues

[Amer7]

Hi, I'm struggling with simple stuff

How do I actually ask for like: Input σ₁², and to store that number in like a1? I couldnt get to show symbols like σ₁², and when i ask to store it in a1 I have a syntax error ?

I got it like this INPUT(A, "", "Input σ₁²");
INPUT(B, "", "Input σ₂²");
INPUT(C, "", "Input σ₁₂");
INPUT(F, "", "Input F(α,2,f)");

To work
How do i make these display, one under other in input screen.