#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using P = pair<ll,ll>;
#define rep(i, n) for(int i = 0; i < n; i++)
#define all(x) (x).begin(),(x).end()
template<class T>bool chmin(T&a, const T&b){if(a>b){a=b;return 1;}return 0;}
template<class T>bool chmax(T&a, const T&b){if(a<b){a=b;return 1;}return 0;}

int main(){
    ll n,k,m;
    cin >> n >> k >> m;
    ll ans = 0, k2 = n-k;

    while(n){
        ans += n / m;
        n /= m;
    }
    while(k){
        ans -= k / m;
        k /= m;
    }
    while(k2){
        ans -= k2 / m;
        k2 /= m;
    }
    cout << ans << endl;
    return 0;
}