JavaScript program to calculate trapezoid circumference

Following program shows you how to calculate trapezoid circumference.
This program gets trapezoid bases and sides from user and calculates circumference and prints it using following formula
Circumference = base1 + base2 + side1 +side2

var trapezoidBase1 = parseInt(prompt("Please enter base1 of trapezoid:"));
var trapezoidBase2 = parseInt(prompt("Please enter base2 of trapezoid:"));
var trapezoidSide1 = parseInt(prompt("Please enter side1 of trapezoid:"));
var trapezoidSide2 = parseInt(prompt("Please enter side2 of trapezoid:"));
var circumferenceOfTrapezoid = trapezoidBase1 + trapezoidBase2 + trapezoidSide1 + trapezoidSide2;
console.log("Circumference of trapezoid is: " + circumferenceOfTrapezoid);

Output:

Please enter base1 of trapezoid:
3
Please enter base2 of trapezoid:
4
Please enter side1 of trapezoid:
8
Please enter side2 of trapezoid:
10
Circumference of trapezoid is: 25.0