#include<iostream>
#include<vector>
#include<algorithm>
#include<functional>
#include<queue>
#include<stack>
#include<set>
#include<climits>
#include<cstdlib>
#include<cmath>
#include<string>

using namespace std;

#define INF 1 << 29
#define LL long long int

LL const MOD = 1000000007;

int main(){
    cin.tie(0);
    ios::sync_with_stdio(false);

    LL n;
	cin >> n;

	vector<bool> sosu(n+1,true);

	sosu[0] = sosu[1] = false;

	for(int i = 2; i < n+1; i++){
		if(sosu[i]){
			for(int j = 2*i; j < n+1; j += i){
				sosu[j] = false;
			}
		}
	}

	LL ans = 0;

	for(int i = 0; i < n+1; i++){
		if(sosu[i]){
			ans += i;
		}
	}

	cout << ans << endl;
    
    return 0;
}