#![allow(non_snake_case)]
#![allow(unused_imports)]
#![allow(unused_macros)]
#![allow(clippy::needless_range_loop)]
#![allow(clippy::comparison_chain)]
#![allow(clippy::nonminimal_bool)]
#![allow(clippy::neg_multiply)]
#![allow(dead_code)]
use std::cmp::Reverse;
use std::collections::{BTreeMap, BTreeSet, BinaryHeap, VecDeque};

#[derive(Default)]
struct Solver {}
impl Solver {
    fn solve(&mut self) {
        // input! {
        //     A: chars,
        //     B: chars
        // }

        // let a: usize = A[A.len() - 1].to_string().parse().unwrap();
        // let b: usize = B[B.len() - 1].to_string().parse().unwrap();

        // if a % 2 == 0 || b % 2 == 0 {
        //     println!("Even");
        // } else {
        //     println!("Odd");
        // }

        input! {
            mut H: usize,
            A: usize
        }

        let mut ans = 0_usize;
        let mut p = 1_usize;
        while H > 0 {
            ans += p;
            H /= A;
            p *= 2;
        }
        println!("{}", ans);
    }
}

trait Bound<T> {
    fn lower_bound(&self, x: &T) -> usize;
    fn upper_bound(&self, x: &T) -> usize;
}

impl<T: PartialOrd> Bound<T> for [T] {
    fn lower_bound(&self, x: &T) -> usize {
        let (mut low, mut high) = (0, self.len());
        while low + 1 < high {
            let mid = (low + high) / 2;
            if self[mid] < *x {
                low = mid;
            } else {
                high = mid;
            }
        }
        if self[low] < *x {
            low + 1
        } else {
            low
        }
    }

    fn upper_bound(&self, x: &T) -> usize {
        let (mut low, mut high) = (0, self.len());
        while low + 1 < high {
            let mid = (low + high) / 2;
            if self[mid] <= *x {
                low = mid;
            } else {
                high = mid;
            }
        }
        if self[low] <= *x {
            low + 1
        } else {
            low
        }
    }
}

#[macro_export]
macro_rules! max {
    ($x: expr) => ($x);
    ($x: expr, $( $y: expr ),+) => {
        std::cmp::max($x, max!($( $y ),+))
    }
}
#[macro_export]
macro_rules! min {
    ($x: expr) => ($x);
    ($x: expr, $( $y: expr ),+) => {
        std::cmp::min($x, min!($( $y ),+))
    }
}

fn main() {
    std::thread::Builder::new()
        .stack_size(128 * 1024 * 1024)
        .spawn(|| Solver::default().solve())
        .unwrap()
        .join()
        .unwrap();
}

#[macro_export]
macro_rules! input {
    () => {};
    (mut $var:ident: $t:tt, $($rest:tt)*) => {
        let mut $var = __input_inner!($t);
        input!($($rest)*)
    };
    ($var:ident: $t:tt, $($rest:tt)*) => {
        let $var = __input_inner!($t);
        input!($($rest)*)
    };
    (mut $var:ident: $t:tt) => {
        let mut $var = __input_inner!($t);
    };
    ($var:ident: $t:tt) => {
        let $var = __input_inner!($t);
    };
}

#[macro_export]
macro_rules! __input_inner {
    (($($t:tt),*)) => {
        ($(__input_inner!($t)),*)
    };
    ([$t:tt; $n:expr]) => {
        (0..$n).map(|_| __input_inner!($t)).collect::<Vec<_>>()
    };
    ([$t:tt]) => {{
        let n = __input_inner!(usize);
        (0..n).map(|_| __input_inner!($t)).collect::<Vec<_>>()
    }};
    (chars) => {
        __input_inner!(String).chars().collect::<Vec<_>>()
    };
    (bytes) => {
        __input_inner!(String).into_bytes()
    };
    (usize1) => {
        __input_inner!(usize) - 1
    };
    ($t:ty) => {
        $crate::read::<$t>()
    };
}

#[macro_export]
macro_rules! println {
    () => {
        $crate::write(|w| {
            use std::io::Write;
            std::writeln!(w).unwrap()
        })
    };
    ($($arg:tt)*) => {
        $crate::write(|w| {
            use std::io::Write;
            std::writeln!(w, $($arg)*).unwrap()
        })
    };
}

#[macro_export]
macro_rules! print {
    ($($arg:tt)*) => {
        $crate::write(|w| {
            use std::io::Write;
            std::write!(w, $($arg)*).unwrap()
        })
    };
}

#[macro_export]
macro_rules! flush {
    () => {
        $crate::write(|w| {
            use std::io::Write;
            w.flush().unwrap()
        })
    };
}

pub fn read<T>() -> T
where
    T: std::str::FromStr,
    T::Err: std::fmt::Debug,
{
    use std::cell::RefCell;
    use std::io::*;

    thread_local! {
        pub static STDIN: RefCell<StdinLock<'static>> = RefCell::new(stdin().lock());
    }

    STDIN.with(|r| {
        let mut r = r.borrow_mut();
        let mut s = vec![];
        loop {
            let buf = r.fill_buf().unwrap();
            if buf.is_empty() {
                break;
            }
            if let Some(i) = buf.iter().position(u8::is_ascii_whitespace) {
                s.extend_from_slice(&buf[..i]);
                r.consume(i + 1);
                if !s.is_empty() {
                    break;
                }
            } else {
                s.extend_from_slice(buf);
                let n = buf.len();
                r.consume(n);
            }
        }
        std::str::from_utf8(&s).unwrap().parse().unwrap()
    })
}

pub fn write<F>(f: F)
where
    F: FnOnce(&mut std::io::BufWriter<std::io::StdoutLock>),
{
    use std::cell::RefCell;
    use std::io::*;

    thread_local! {
        pub static STDOUT: RefCell<BufWriter<StdoutLock<'static>>> =
            RefCell::new(BufWriter::new(stdout().lock()));
    }

    STDOUT.with(|w| f(&mut w.borrow_mut()))
}