#include <bits/stdc++.h>
using namespace std;

bool isPrime( long long x )
{
	if( x < 2 ) return false;
	if( x == 2 ) return true;
	if( x % 2 == 0 ) return false;
	for( long long i = 3; i * i <= x; i += 2 ) {
		if( x % i == 0 ) return false;
	}
	return true;
}

int main()
{
	int N;
	cin >> N;

	int ans = 0;
	for( int n = 1; n <= N; n++ ) {
		if( isPrime( n ) == false ) continue;
		ans += n;
	}

	cout << ans << endl;
}