use proconio::input;

#[allow(dead_code)]
mod util {
    //! よく使われるユーティリティ関数をまとめたモジュール

    /// 最小値と最大値を更新するトレイト
    ///
    /// # Examples
    ///
    /// ```
    /// use cp_lib_rs::util::ChangeMinMax;
    ///
    /// let mut x = 10;
    /// assert!(x.change_min(3));
    /// assert_eq!(x, 3);
    /// ```
    #[allow(dead_code)]
    pub trait ChangeMinMax {
        fn change_min(&mut self, v: Self) -> bool;
        fn change_max(&mut self, v: Self) -> bool;
    }

    impl<T: PartialOrd> ChangeMinMax for T {
        fn change_min(&mut self, v: T) -> bool {
            *self > v && {
                *self = v;
                true
            }
        }

        fn change_max(&mut self, v: T) -> bool {
            *self < v && {
                *self = v;
                true
            }
        }
    }

    /// 多次元配列を作成する
    ///
    /// # Examples
    ///
    /// ```
    /// use cp_lib_rs::mat;
    ///
    /// let a = mat![0; 4; 3];
    /// assert_eq!(a, vec![vec![0; 3]; 4]);
    /// ```
    #[macro_export]
    macro_rules! mat {
	($($e:expr),*) => { vec![$($e),*] };
	($($e:expr,)*) => { vec![$($e),*] };
	($e:expr; $d:expr) => { vec![$e; $d] };
	($e:expr; $d:expr $(; $ds:expr)+) => { vec![mat![$e $(; $ds)*]; $d] };
}
}

fn main() {
    input! {
        n: usize,
    }

    let mut sum = 0;

    for i in 1..=n {
        sum += i;
    }

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