Javascript help - Credit hour calculator

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Javascript

Hello. I am new to Javascript and I want to make a credit hour calculator. I have it almost complete, but I want it to calculate the total number of credit hours: for example if I put in three 3 credit hours that is 9 credit hours total. I know this might sound confusing but right now all it does is add up the total number. Right now there are three text fields called 1 credit hour, 2 credit hours, and 3 credit hours. For example if someone were to put in that they were taking 1 1credit hour course, 2 2credit hour course and 3 3credit hour courses I want the total to come out to be 14 credit hours. Here is my JS Fiddle file for it so you can make more sense of it: JS Fiddle

Also Here is my code I have so far:

function doCalc() 
{
var value1 = document.getElementById("credit1").value;
var value2 = document.getElementById("credit2").value;
var value3 = document.getElementById("credit3").value;
var total = Number(value1) + Number(value2) + Number(value3);
document.getElementById("output").value = total;
}

1 credit hour: <input type="number" id="credit1">
<br /> 

2 credit hour: <input type="number" id="credit2">
<br /> 

3 credit hour: <input type="number" id="credit3">
<br /> 

Total: <input id="output">
<br />

<button >Calculate</button>