#include<bits/stdc++.h> using namespace std; int main() { int n; int day=1; int sd; int money=0; cin>>n; while(sd<=n) { sd=day*(day+1)/2; if(sd>n) { break; } money+=day*day; day++; } money+=(n-(day-1)*day/2)*day; cout<<money<<endl; return 0; }