Main function

Question

I don't understand the purpose of this function and how to complete it
function main() {
var num1 = parseInt(readLine(),10);
var num2 = parseInt(readLine(),10);
var num3 = parseInt(readLine(),10);
var average;

Answer 1

This program should calculate the average value of the 3 numbers given
var average = (num1 + num2 + num3) / 3;