Hi, I have started learning Rust and am following the tutorial book.

right now I am trying to generate the nth Fibonacci number (using loop based approach), The problem is my variables in the loop do not get updated as I expect them to, in the first iteration i can see that the second_last_number is updated but then all variable remain the same in all iterations

```
use std::io;
fn main() {
println!("Enter number : ");
let mut number = String::new();
io::stdin().read_line(&mut number)
.expect("Failed to read line");
let number: u32 = number.trim().parse()
.expect("Please type a number!");
let last_number: i32 = 1;
let second_last_number: i32 = 0;
let result: i32 = 0;
for x in 1..number + 1{
println!("index : {}", x);
let result = last_number + second_last_number;
println!("result : {}", result);
let second_last_number = last_number;
println!("second : {}", second_last_number);
let last_number = result;
println!("last : {}", last_number);
}
println!("{} fibonnaci number is {}", number, result);
}
```