Overflow

main.rs

/// So I have this code snippet
extern crate num;
use num::{BigUint, Zero, One};
use std::mem::replace;

fn main() {
    let mut f0: BigUint = 100;
    let mut f1: BigUint = 100;
    for _ in (0..100) {
        if f0 <= 1 {
            break;
        }
        f0 -= 1;
        // This is a low cost way of swapping f0 with f1 and f1 with f2.
        f1 *= f0;
    }
    println!("{}", f1);
}
/// I used BigInt because if I used i64's I would get an overflow error, but the problem is
/// That I cant use binary operations with BigInts, is there a workaround or another soltuion
/// to this tragic predicament??