#include<bits/stdc++.h>
using namespace std;
using ll = long long;
#define rep(i,m,n) for(int i=m; i<n; ++i)
#define repl(i,m,n) for(ll i=m; i<n; ++i)

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

    vector<bool> is_p(N+1, true);
    is_p[0] = is_p[1] = false;
    for(int i = 2; i <= N; ++i){
        if(!is_p[i]) continue;
        for(int j = i+i; j <= N; j += i){
            is_p[j] = false;
        }
    }

    int ans = 0;
    rep(i, 0, N+1){
        if(is_p[i]) ans += i;
    }
    cout << ans << endl;

    return 0;
}