#define rep(i,n) for(int i=0;i<(int)(n);i++)
#define ALL(v) v.begin(),v.end()
typedef long long ll;
 
#include<bits/stdc++.h>
using namespace std;

#include <boost/multiprecision/cpp_dec_float.hpp>
#include <boost/multiprecision/cpp_int.hpp>
namespace mp = boost::multiprecision;
using Bint = mp::cpp_int;
 
int main(){
  ios::sync_with_stdio(false);
  std::cin.tie(nullptr);
  
  Bint n,k,m;
  cin>>n>>k>>m;
  
  Bint ans=0;
  Bint t=m;
  while(n/t>=1){
    ans+=n/t;
    t*=m;
  }
  t=m;
  while(k/t>=1){
    ans-=k/t;
    t*=m;
  }
  t=m;
  while((n-k)/t>=1){
    ans-=(n-k)/t;
    t*=m;
  }
  cout<<ans<<endl;
  
  return 0;
}