Fib

fn fib(fib_num: usize) -> u128 {
if fib_num <= 2 {
return 1;
}

let fib_nums: Vec<u128> = (2..fib_num).fold(
    vec![1, 1],
    |prev, _| vec![prev[1], prev.iter().sum()],
);

*fib_nums.last().unwrap()

}

fn main() {
println!("Fibonacci number at position 100: {}", fib(100));
}