use std::io::{self, BufRead, BufReader, BufWriter, Write};

fn main() {
    let stdin = io::stdin();
    let mut stdin = BufReader::new(stdin.lock());
    let stdout = io::stdout();
    let mut stdout = BufWriter::new(stdout.lock());
    run(&mut stdin, &mut stdout);
}

fn run<R, W>(input: &mut R, output: &mut W)
where
    R: BufRead,
    W: Write,
{
    let mut n = String::new();
    input.read_line(&mut n).unwrap();
    let n: u32 = n.trim().parse().unwrap();

    let sum: u32 = (1..=n).sum();

    writeln!(output, "{}", sum).unwrap();
}