fn main() {
    /* mutability */
    let mut x = 5;
    println!("The variable of x is: {}", x);
    x = 6;
    println!("The variable of x is: {}", x);

    /* shadowing */
    let x = 5;

    let x = x + 1;

    let x = x * 2;

    println!("The value of x is: {}", x);
}