#include<bits/stdc++.h> using namespace std; long long n,m,p,tmp,sum; int main() { cin>>n>>m>>p; tmp=1; for(int i=1;i<=p;i++) { //cout<<sum<<endl; if(tmp*m>n) { i--; sum+=(p-i)*n; break; } tmp*=m; sum+=tmp; } cout<<sum<<endl; return 0; }