#include <iostream>
using namespace std;

const int maxn =10000000;
int n,size ;
int prime[maxn+5];
bool vis[maxn+5];

int main() {
	cin >>n;
	size = 0;
	for (int i= 2; i<=n; ++i) {
		if (!vis[i]) {
			size = size + 1;
			prime[size]= i;
		}
		for (int j=1; i*prime[j]<=n; ++j) {
			vis[i * prime[j]]= 1;
			if (i % prime[j]==0)
				break ;
		}
	}
	int sum = 0;
	for (int i=1; i<=size; ++i)
		sum=sum + prime[i];
	cout<<sum<<endl;
	return 0;
}