//! # Bundled libraries
//!
//! - `arithmetic_series 0.1.0 (git+https://github.com/ia7ck/rust-competitive-programming#b60dc67706797611e680510aa6492f6397a2e104)` licensed under **missing** as `crate::__cargo_equip::crates::arithmetic_series`
//! - `input_i_scanner 0.1.0 (git+https://github.com/ia7ck/rust-competitive-programming#b60dc67706797611e680510aa6492f6397a2e104)`   licensed under **missing** as `crate::__cargo_equip::crates::input_i_scanner`

pub use __cargo_equip::prelude::*;

use arithmetic_series::arithmetic_series;
use input_i_scanner::InputIScanner;

fn main() {
    let stdin = std::io::stdin();
    let mut _i_i = InputIScanner::from(stdin.lock());

    macro_rules! scan {
        (($($t: ty),+)) => {
            ($(scan!($t)),+)
        };
        ($t: ty) => {
            _i_i.scan::<$t>() as $t
        };
        (($($t: ty),+); $n: expr) => {
            std::iter::repeat_with(|| scan!(($($t),+))).take($n).collect::<Vec<_>>()
        };
        ($t: ty; $n: expr) => {
            std::iter::repeat_with(|| scan!($t)).take($n).collect::<Vec<_>>()
        };
    }

    let n = scan!(u64);
    // 1 + 2 + 3 + ...
    let ans = arithmetic_series(1, (n + 1) / 2, 1).unwrap();
    println!("{}", ans);
}

// The following code was expanded by `cargo-equip`.

#[rustfmt::skip]
#[allow(unused)]
mod __cargo_equip {
    pub(crate) mod crates {
        pub mod arithmetic_series {pub fn arithmetic_series<T:Int>(a:T,n:T,d:T)->Option<T>{assert!(n.is_positive());let last=d.checked_mul(n.decrement())?.checked_add(a)?;a.checked_add(last)?.checked_mul(n)?.checked_div(T::two())}pub trait Int:Copy+Ord{fn is_positive(self)->bool;fn decrement(self)->Self;fn checked_add(self,rhs:Self)->Option<Self>;fn checked_mul(self,rhs:Self)->Option<Self>;fn checked_div(self,rhs:Self)->Option<Self>;fn two()->Self;}macro_rules!impl_int{($($t:ty),+)=>{$(impl Int for$t{fn is_positive(self)->bool{self>=1}fn decrement(self)->Self{self-1}fn checked_add(self,rhs:Self)->Option<Self>{self.checked_add(rhs)}fn checked_mul(self,rhs:Self)->Option<Self>{self.checked_mul(rhs)}fn checked_div(self,rhs:Self)->Option<Self>{self.checked_div(rhs)}fn two()->Self{2}})+};}impl_int!(i32,i64,u32,u64,usize);}
        pub mod input_i_scanner {use std::fmt;use std::io;use std::str;pub struct InputIScanner<R>{r:R,l:String,i:usize,}impl<R:io::BufRead>InputIScanner<R>{pub fn new(reader:R)->Self{Self{r:reader,l:String::new(),i:0,}}pub fn scan<T>(&mut self)->T where T:str::FromStr,<T as str::FromStr>::Err:fmt::Debug,{self.skip_blanks();assert!(self.i<self.l.len());assert_ne!(&self.l[self.i..=self.i]," ");let rest=&self.l[self.i..];let len=rest.find(' ').unwrap_or_else(| |rest.len());let val=rest[..len].parse().unwrap_or_else(|e|panic!("{:?}, attempt to read `{}`",e,rest));self.i+=len;val}fn skip_blanks(&mut self){loop{match self.l[self.i..].find(|ch|ch!=' '){Some(j)=>{self.i+=j;break;}None=>{let mut buf=String::new();let num_bytes=self.r.read_line(&mut buf).unwrap_or_else(|_|panic!("invalid UTF-8"));assert!(num_bytes>0,"reached EOF :(");self.l=buf.trim_end_matches('\n').trim_end_matches('\r').to_string();self.i=0;}}}}}impl<'a>From<&'a str>for InputIScanner<&'a[u8]>{fn from(s:&'a str)->Self{Self::new(s.as_bytes())}}impl<'a>From<io::StdinLock<'a> >for InputIScanner<io::BufReader<io::StdinLock<'a> > >{fn from(stdin:io::StdinLock<'a>)->Self{Self::new(io::BufReader::new(stdin))}}}
    }

    pub(crate) mod macros {
        pub mod arithmetic_series {}
        pub mod input_i_scanner {}
    }

    pub(crate) mod prelude {pub use crate::__cargo_equip::crates::*;}

    mod preludes {
        pub mod arithmetic_series {}
        pub mod input_i_scanner {}
    }
}