#![allow(unused_imports)]
use std::cmp::*;
use std::collections::*;
use std::io::Write;
use std::ops::Bound::*;

#[allow(unused_macros)]
macro_rules! debug {
    ($($e:expr),*) => {
        #[cfg(debug_assertions)]
        $({
            let (e, mut err) = (stringify!($e), std::io::stderr());
            writeln!(err, "{} = {:?}", e, $e).unwrap()
        })*
    };
}

fn main() {
    let v = read_vec::<i128>();
    let (n, k, m) = (v[0], v[1], v[2]);

    let mut ans = 0;
    let mut x = 1;
    let mut m2 = m;
    for i in 0..=50 {
        if m2 > n {
            break;
        }
        let c1 = count(k, m2);
        let c2 = count(n, m2);
        let c3 = count(n - k, m2);
        let d1 = (0..=50).map(|x| c2[x] - c3[x]).collect::<Vec<_>>();

        let cc = (1..=50).map(|x| c1[x] * x as i128).sum::<i128>();
        let dc = (1..=50).map(|x| d1[x] * x as i128).sum::<i128>();
        if dc > cc {
            ans = x;
        }

        m2 *= m;
        x += 1;
    }

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

fn count(k: i128, m: i128) -> Vec<i128> {
    let mut start = 0;
    let mut coef = 1;
    while coef * m <= k {
        start += 1;
        coef *= m;
    }

    let mut coef2 = coef;
    let mut start2 = start;
    let mut count2 = 0;
    let mut ret = vec![0; 51];
    while coef2 >= 1 {
        let cur_count = k / coef2 - count2;
        ret[start2 as usize] = cur_count;
        count2 += cur_count;
        coef2 /= m;
        start2 -= 1;
    }
    ret
}

fn read<T: std::str::FromStr>() -> T {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).ok();
    s.trim().parse().ok().unwrap()
}

fn read_vec<T: std::str::FromStr>() -> Vec<T> {
    read::<String>()
        .split_whitespace()
        .map(|e| e.parse().ok().unwrap())
        .collect()
}