struct Fibonacci {
    current: u64,
    next: u64
}

impl Iterator for Fibonacci {
    type Item = u64;
    fn next(&mut self) -> Option<u64> {
        let n = self.current + self.next;
        self.current = self.next;
        self.next = n;
        Some(self.current)
    }
}

fn main() {
    let f = Fibonacci {
        current: 1,
        next: 1
    };
    for n in f.take(91) {
        println!("{}", n);
    }
}