#include <bits/stdc++.h> #define int long long using namespace std; inline int read(){ int x=0;bool f=1;char c=getchar(); while(c>'9'||c<'0'){if(c=='-')f=0;c=getchar();} while(c>='0'&&c<='9'){x=(x<<3)+(x<<1)+(c^48);c=getchar();} return f?x:-x; } int n,k,p,ans; signed main(){ //freopen("set.in","r",stdin); //freopen("set.out","w",stdout); n=read(),k=read(),p=read(); int i,j; for(i=0,j=k;i<=p&&j<=n;j*=k,i++) ans+=j; ans=ans+n*(p-i); printf("%lld\n",ans); return 0; }