How can i put “you are entering a number” right below the input box when i select input box?

        .Input{
        background-color:grey;
        }
        .Input:focus {
        background-color: white;
        }
    

Enter the first number:

Enter the second number:

Enter the third number:

Enter the fourth number:

Enter the fifth number:

Submit

function get_product_of_inputs() {
    var a = document.getElementById("a").value;
    var b = document.getElementById("b").value;
    var c = document.getElementById("c").value;
    var d = document.getElementById("d").value;
    var e = document.getElementById("e").value;
    var f = a*b*c*d*e;
    console.log(f);
    document.getElementById("Submit").innerHTML= ("Product of all the numbers are "+f);
}

I am literally trying to put “you are entering a number” when someone select the input field. what can i do?
Please help me out. I am a bit confused at this point?