use std::io;
use std::io::Stdin;

// コピペ
struct Input {
    n: i32,
}

fn main() {
    let mut stdin = io::stdin();
    let input = read_input(&mut stdin);

    let result = (1..input.n + 1).fold(0, |a, b| a + b);
    println!("{}", result)
}

// コピペ
fn read_input(stdin: &mut Stdin) -> Input {
    let mut s = String::new();
    stdin.read_line(&mut s).expect("can't read input.");

    let n = s.trim_end().parse::<i32>().expect("can't convert to integer");
    Input { n }
}