use std::io::{BufRead, BufReader, stdin};

type Result<T> = std::result::Result<T, Box<std::error::Error>>;

fn get_number<R: BufRead>(reader: &mut R) -> Result<u32> {
    let mut buf = String::new();
    reader.read_line(&mut buf)?;

    let n: u32 = buf.trim().parse()?;
    Ok(n)
}

fn main() {
    let mut reader = BufReader::new(stdin());
    let n = get_number(&mut reader).expect("failed to get number");

    let sum: u32 = (1..n+1).sum();
    println!("{}", sum);
}