#include <bits/stdc++.h>
    using namespace std;
    #include <math.h>
    #include <iomanip>
    #include <cstdint>
    #include <string>
    #include <sstream>
    #include <random>
    template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
    template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
    #define rep(i,n) for (int i = 0; i < (n); ++i)
    typedef long long ll;
    typedef unsigned long long ull;
    using P=pair<ll,ll>;
    const int INF=1001001001;
    const ll INFL=1e18;
    const int mod=1e9+7;
    
    ll f(ll x,ll m){
        ll cnt=0;
        while(x){
            cnt+=x/m;
            x/=m;
        }
        return cnt;
    }
    void solve(){
        ll n,k,m;
        cin>>n>>k>>m;
        ll L=f(n,m)-f(n-k,m),R=f(k,m);
        cout<<L-R<<endl;
    }  

    int main(){
        ios_base::sync_with_stdio(false);
        cin.tie(NULL);
        
        solve();  
        
        return 0;
    }