#include <bits/stdc++.h>
using namespace std;
using ll = long long;
#define all(A) A.begin(),A.end()
using vll = vector<ll>;
#define rep(i, n) for (long long i = 0; i < (long long)(n); i++)
int main() {
    ll N,K,M,an=0;
    cin>>N>>K>>M;
    ll A=N-K;
    rep(i,70)an+=(N/=M)-(K/=M)-(A/=M);
    cout<<an<<endl;
}