use std::io;
use std::str;

pub trait ParseLine {
    fn parse_line<R: io::BufRead>(s: &mut Input<R>) -> Self;
}

macro_rules! impl_parse_line {
    ($($t:ty),*) => {
        $(impl ParseLine for $t {
            fn parse_line<R: io::BufRead>(s: &mut Input<R>) -> Self {
                s.token()
            }
        })*
    };
}
impl_parse_line!(
    u8, u16, u32, u64, u128, usize, i8, i16, i32, i64, i128, isize, f32, f64, String, char
);

macro_rules! impl_parse_line_tuple {
    ($($t:ident),*) => {
        impl<$($t: ParseLine),*> ParseLine for ($($t,)*) {
            fn parse_line<R: io::BufRead>(s: &mut Input<R>) -> Self {
                ($($t::parse_line(s),)*)
            }
        }
    };
}

impl_parse_line_tuple!(T0, T1);
impl_parse_line_tuple!(T0, T1, T2);
impl_parse_line_tuple!(T0, T1, T2, T3);
impl_parse_line_tuple!(T0, T1, T2, T3, T4);
impl_parse_line_tuple!(T0, T1, T2, T3, T4, T5);
impl_parse_line_tuple!(T0, T1, T2, T3, T4, T5, T6);
impl_parse_line_tuple!(T0, T1, T2, T3, T4, T5, T6, T7);
impl_parse_line_tuple!(T0, T1, T2, T3, T4, T5, T6, T7, T8);
impl_parse_line_tuple!(T0, T1, T2, T3, T4, T5, T6, T7, T8, T9);

pub struct Input<R> {
    reader: R,
    buffer: Vec<String>,
}

// impl Input<std::io::StdinLock<'static>> {
//     pub fn stdio() -> Self {
//         let stdin = std::io::stdin();
//         let scan = Input::new(stdin.lock());

//         scan
//     }
// }

impl<R: io::BufRead> Input<R> {
    pub fn new(reader: R) -> Self {
        Self {
            reader,
            buffer: vec![],
        }
    }

    pub fn token<T: str::FromStr>(&mut self) -> T {
        loop {
            if let Some(token) = self.buffer.pop() {
                return token.parse().ok().expect("Failed parse");
            }
            let mut input = String::new();
            self.reader.read_line(&mut input).expect("Failed read");
            self.buffer = input.split_whitespace().rev().map(String::from).collect();
        }
    }

    pub fn read<T: ParseLine>(&mut self) -> T {
        ParseLine::parse_line(self)
    }

    pub fn usize1(&mut self) -> usize {
        self.token::<usize>() - 1
    }

    pub fn isize1(&mut self) -> isize {
        self.token::<isize>() - 1
    }

    pub fn chars(&mut self) -> Vec<char> {
        self.token::<String>().chars().collect()
    }

    pub fn vec<T: ParseLine>(&mut self, n: usize) -> Vec<T> {
        (0..n).map(|_| ParseLine::parse_line(self)).collect()
    }
}

fn main() {
    let mut input = Input::new(std::io::stdin().lock());

    let n: usize = input.read();

	let mut total = 0;
	
	for i in 1..=n{
		total += i;
	}

    println!("{}", total);
}