#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define rrep(i,n) for(int i = 1; i <= (n); ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<P> vp;
#define dame { puts("-1"); return 0;}
#define yn {puts("Yes");}else{puts("No");}


/*
    Max_Prime以下の素数をprimes[]に格納
*/

const int Max_Prime = 1000000;
vector<int> tmp_primes;
vector<int> primes;

void PrimeInit() {
    rep(i,Max_Prime-1){
        tmp_primes.push_back(i+2);
    }

    int rem = Max_Prime - 1;
    int count = 0;
    while(rem>0){
        if(tmp_primes[0]*tmp_primes[0] > Max_Prime){
            rep(i,rem){
                primes.push_back(tmp_primes[i]);
                count++;
            }
            break;
        }
        primes.push_back(tmp_primes[0]);
        count++;
        int count2 = 0;
        srep(i,1,rem){
            if(tmp_primes[i] % primes[count-1] != 0){
                tmp_primes[count2] = tmp_primes[i];
                count2++;
            }
        }
        rem = count2;
    }
}

int main(){
    PrimeInit();

    int n;
    cin >> n;

    int ans = 0;
    rep(i,2000){
        if(primes[i] > n)break;
        ans += primes[i];
    }
    cout << ans << endl;
    return 0;
}