func simpleFunction() {
    print("This is a simple function")
}

simpleFunction()
//Output: This is a simple function

func secondFunction() {
    let friend1 = "Mike"
    let friend2 = "Lisa"

    print("My best friends are \(friend1) and \(friend2)")
}

secondFunction()
//Output: My best friends are Mike and Lisa

func oneLastFunction() {
    let pi = Double.pi

    print("The square root of pi is \(pi.squareRoot())")
}

oneLastFunction()
//Output: The square root of pi is 1.7724538509055159