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

int main(){
	cin.tie(0),ios::sync_with_stdio(false);
	int n; cin>>n;
	vector<bool>v(n+1,true);
	for(int i=2;i*i<=n;++i){
		if(!v.at(i))continue;
		for(int j=i*i;j<=n;j+=i){
			v.at(j)=false;
		}
	}
	int ans=0;
	for(int i=2;i<=n;++i)if(v.at(i))ans+=i;
	cout<<ans<<"\n"s;
}