I am trying to grab the value from an html input, and I am having trouble getting it to work, from what I was looking at doing my own research, it looks like I have the correct syntax? So I am confused.

when I console log the value, it looks like its not actually getting the value of the input. 

```
let btn = document.getElementById("btn");
let grade = document.getElementById("gradeNum").value;

function getGrade() {
    console.log(grade);

    if (grade >= 90) {
        document.getElementById("gradeLetter").innerHTML = "You got an A!";
    } else if (grade < 90 && grade >= 80) {
        document.getElementById("gradeLetter").innerHTML = "You got a B!";
    } else if (grade < 80 && grade >= 70) {
        document.getElementById("gradeLetter").innerHTML = "You got a C!";
    } else if (grade < 70) {
        document.getElementById("gradeLetter").innerHTML = "You got an F! Study more!";
    }
};

```