#include<iostream>
#include<vector>
#include<algorithm>
#include<cstring>
#include<cassert>
#include<cmath>
#include<ctime>
#include<iomanip>
#include<numeric>
#include<stack>
#include<queue>
#include<map>
#include<unordered_map>
#include<set>
#include<unordered_set>
#include<bitset>
#include<random>
using namespace std;
long long N,K,M;
long long f(long long X)
{
	long long res = 0;
	X /= M;
	while(X) res += X,X /= M;
	return res;
}
void solve()
{
	cin >> N >> K >> M;
	long long ans = f(N)-f(N-K)-f(K);
	cout << ans << endl;
}
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	//tanosimu
	int tt = 1;
	//cin >> tt;
	while(tt--) solve();
}