#include<bits/stdc++.h>
using namespace std;
#define io std::ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define file(name) {freopen(name".INP","r",stdin);freopen(name".OUT","w",stdout);}
int main (){
    io;file("SUM");
    int n;cin>>n;
    int x=n/7;
    int sum=((x*(x+1))/2)*7;
    cout<<sum;
return 0;}