fn main() {
    let a = 10;
    let a = a + 5;
    let a = a * 10;

    let mut a = 10;
    a = a + 5;
    a = a * 10;

    let hello = "Hello, world!";
    let hello_length = hello.len();
    
    let hello = "Hello, world!";
    let hello = hello.len();
}