fn one() {
    let mut count : u64 = 0;
    let until = 1e8 as u64;
    for i in 1..until {
        let s = i.to_string();
        if s.contains("3") {
            count+=1;
        }
    }
    println!("Count until {}: {}", until, count);

}

fn two() {
    let mut count : u64 = 0;
    let until = 1e8 as u64;
    let mut s = String::with_capacity(10);
    for i in 1..until {
        s.clear();
        use std::fmt::Write;
        write!(s, "{}", i).unwrap();
        if s.contains("3") {
            count+=1;
        }
    }
    println!("Count until {}: {}", until, count);
}