//No.713 素数の和
#include<iostream>
#include<math.h>
using namespace std;
void col_pnum(bool*,int);
int main()
{
	int N;
	cin >> N;
	bool* pnum = new bool[N+1];
	for (int i = 0; i <= N; i++) {
		pnum[i] = true;
	}
	col_pnum(pnum, N);
	int cnt = 0;
	for (int i = 0; i <= N; i++) {
		if (pnum[i] == true) {
			cnt += i;
		}

	}
	cout << cnt;
	return 0;
}

//Nまでの素数を求める
void col_pnum(bool *_pnum,int _N) {
	_pnum[0] = _pnum[1] = false;
	for (int i=2; i<_N; i++) {
		if (_pnum[i] == false)continue;
		for (int j=2; i*j <= _N; j++) {
			_pnum[i*j] = false;
		}
	}
	return;
}