#include <bits/stdc++.h>
#define rep(i,a,b) for(int i=a;i<(b);++i)
#define erep(i,a,b) for(int i=a;i<=(int)(b);++i)
#define per(i,a,b) for(int i=(a);i>(b);--i)
#define eper(i,a,b) for(int i=(a);i>=b;--i)
#define pb push_back
#define mp make_pair
#define INF (1<<30)-1
#define MOD 1000000007
#define all(x) (x).begin(),(x).end()
#define vii vector<int>
#define vll vector<long long>
using namespace std;
typedef long long ll;
typedef pair<int,int> Pii;
template<class T>bool chmax(T &a, const T &b) { if (a<b) { a = b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a = b; return 1; } return 0; }
int dy[]={0, 0, 1, -1};
int dx[]={1, -1, 0, 0};
int gcd(int a,int b){return b?gcd(b,a%b):a;}
int lcm(int a,int b){return a/gcd(a, b)*b;}

vector<int> makePrimes(int n) {
    vector<int> res, pr(n + 1, 1);
    pr[0] = pr[1] = 0;
    rep(p, 2, sqrt(n) + 2) 
      if (pr[p]) 
      for (int x = p * 2; x <= n; x += p) pr[x] = 0;
    rep(p, 2, n + 1) 
      if (pr[p]) 
        res.push_back(p);
    return res;
}

int n;  
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
    cin >> n;
    ll ans = 0;
    auto prime = makePrimes(n);
    for (auto x : prime) {
        ans += x;
    }
    cout << ans << endl;
    return 0;
}