#define _USE_MATH_DEFINES
#include "bits/stdc++.h"
using namespace std;
#define FOR(i,j,k) for(int (i)=(j);(i)<(int)(k);++(i))
#define rep(i,j) FOR(i,0,j)
#define each(x,y) for(auto &(x):(y))
#define mp make_pair
#define MT make_tuple
#define all(x) (x).begin(),(x).end()
#define debug(x) cout<<#x<<": "<<(x)<<endl
#define smax(x,y) (x)=max((x),(y))
#define smin(x,y) (x)=min((x),(y))
#define MEM(x,y) memset((x),(y),sizeof (x))
#define sz(x) (int)(x).size()
#define RT return
#define vv(a,b,c,d) vector<vector<a> >(b,vector<a>(c,d))
#define vvv(a,b,c,d,e) vector<vector<vector<a> > >(b,vv(a,c,d,e))
using ll = long long;
using pii = pair<int, int>;
using vi = vector<int>;
using vll = vector<ll>;

vector<bool> sieveFlags(int n) {
    vector<bool> f(n + 1);
    for (int i = 3; i <= n; i += 2)f[i] = true;
    for (int i = 3; (long long)i*i <= n; i += 2) {
        if (f[i])for (int j = i * 3; j <= n; j += i)f[j] = false;
    }
    if (n >= 2)f[2] = true;
    return f;
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(20);

    int N;
    cin >> N;
    auto f = sieveFlags(N);
    int re = 0;
    for (int i = 2; i <= N; ++i)if (f[i]) {
        re += i;
    }
    cout << re << endl;
}