#include<bits/stdc++.h> using namespace std; long long n,k,p,ans,cnt; template<typename T>T qpow(T a,T b,T n,T ans=0){ for(a%=n;b;b>>=1)b&1&&(ans=ans*a%n),a=a*a%n; return ans; } int main(){ cin>>n>>k>>p; for(long long ki=k;cnt<p&&ki<n;cnt++,ki*=k)ans+=ki; return cout<<ans+n*(p-cnt)<<'\n',0; }