#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <climits>
#include <vector>
#include <bitset>
#include <set>
#include <queue>
#include <stack>
#include <map>
#include <deque>
#include <string>
#include <list>
#include <iterator>
#include <algorithm>
#include <unordered_map>
#define int                long long
#define pb                 push_back
#define pi                 pair<int,int>
#define vi                 vector<int>
#define all(v)             v.begin(),v.end()
#define MOD                1000000007
#define F                  first
#define S                  second
#define FOR(i,r)           for(int i=0;i<r;i++)
#define REP(i,l,r)         for(int i=l;i<r;i++)
#define RER(i,l,r)         for(int i=l;i>=r;i--)
#define print(v)           for(auto i : v)cout << i << ' ';
#define FASTIO             ios::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define mem(arr,k)         memset(arr,k,sizeof(arr));
#define pii                acos(-1.0)
#define PI                 3.1415926535897932385
#define Sin(a)             sin((pi*a)/180)
#define remax(a,b)         a=max(a,b)
#define remin(a,b)         a=min(a,b)
#define bitcount(x)        __builtin_popcountll(x)
#define iceil(n,x)         (((n)-1)/(x)+1)
#define flush              fflush(stdout)
#define pf                 push_front()
#define pob                pop_back()
#define ins                insert
#define mii                map<int,int> 
#define show(x)            for(auto zz:x)cout<<zz<<" ";cout<<"\n";
#define show2(x)           for(auto zz:x)cout<<zz.F<<" "<<zz.S<<"\n";
#define test()             int x;cin >> x;while(x--){solve();}
#define test2()            int x;cin >> x;for(int i=1;i<=x;i++){cout << "Case #" << i << " : ";solve();}
#define watch(x)           cout << (#x) << " is " << (x) << endl
using namespace std;


/* Mathematical Functions */
int power(int x,int y);
bool isPrime(int n);
int modInv(int a,int b);
int gcdExtended(int a,int b,int *x,int* y);
int mpower(int a,int b,int p);

const int inf = (int)1e17;
const int N = (int)1e7+1;
vector<int>spf(N);
void seive(){
	REP(i,1,N){
		spf[i] = i;
	}
	REP(i,4,N){
		spf[i] = 2;
		i++;
	}
	for(int i = 3;i*i <= N;i++){
		if(spf[i] == i){
			for(int j = i*i; j<=N ;j+=i){
				if(spf[j] == j){
					spf[j] = i;
				}
			}
		}
	}
}
int divc(int x){
	int tot = x,prev = -1,pc=0,ls;
	vi bck;
	while(x > 1){
		if(prev == -1 || prev != spf[x]){
			tot *= (pc+1);
			pc = 1;
			prev = spf[x];
		}
		else{
			pc++;
		}
		ls = spf[x];
		x /= spf[x];
	}
	tot *= (pc+1);
	return tot;
}
int32_t main(){

	
	FASTIO;
	seive();
	int x;
	scanf("%lld",&x);
	int ans = 0;
	REP(i,1,x+1){
		ans += divc(i);
	}
	cout << ans << "\n";
    return 0;

}
int modInv(int a, int m)
{
int x, y;
int g = gcdExtended(a, m, &x, &y);
int res = (x%m + m) % m;
return res;
}
 
int gcdExtended(int a, int b, int *x, int *y)
{
if (a == 0){
    *x = 0, *y = 1;
    return b;
  }
  int x1, y1;
  int gcd = gcdExtended(b%a, a, &x1, &y1);
  *x = y1 - (b/a) * x1;
  *y = x1;
  return gcd;
}
 
int mpower(int x, int y, int p)
{
int res = 1;
x = x % p;
while(y > 0){
    if(y & 1) res = (res*x) % p;
      y = y>>1;
      x = (x*x) % p;
    }
    return res;
}
int power(int x, int y)
{
int res = 1;
while (y > 0){
    if (y & 1) res = res*x;
      y = y>>1;
      x = x*x;
    }
    return res;
}
 
bool isPrime(int n)
{
if (n <= 1)  return false;
  if (n <= 3)  return true;
    if (n%2 == 0 || n%3 == 0) return false;
      int p=sqrt(n);
      for(int i=5;i<=p;i=i+6)
        if (n%i == 0 || n%(i+2) == 0)
          return false;
      return true;
}

Measured memory_bytes: 80800