#include <bits/stdc++.h>
#include <atcoder/all>
using namespace std;
using namespace atcoder;
typedef long long ll;
typedef pair<ll,ll> P;
typedef modint998244353 mint;
#define rep(i,a,b) for(ll i=a;i<b;i++)
#define rrep(i,a,b) for(ll i=a;i>=b;i--)
const ll inf=1e18;
ll n;
ll ans;
int main(void){
    cin.tie(0);
    ios::sync_with_stdio(0);
    cin>>n;
    rep(i,2,n+1){
        bool x=true;
        rep(j,2,i){
            if(i%j==0){
                x=false;
            }
        }
        if(x){
            ans+=i;
        }
    }
    cout<<ans<<endl;

}