fn main() {
    let max: u32 = 72 * 60 * 60;
    let mut interval: u32 = 2;
    let mut count: u32 = 1;

    loop {
        println!("interval({}): {}", count, interval);

        if interval > max {
            break;
        }

        count += 1;
        interval = 2u32.pow(count);
    }

    println!("count: {}", count);
}