use proconio::marker::Chars;

fn main() {
    proconio::input! {
        n: u64,
    }
    println!("{}", n as f64 * 3.5);
}

fn proc(n: u64) -> u64 {
    (n / 3 + n / 5) * 2
}

#[cfg(test)]
mod test {
    use super::*;
    #[test]
    fn test() {}
}