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

bool isprime(int n) {
    if (n < 2) return false;
    if (n == 2) return true;
    for (int i = 3; i*i <= n; i += 2) {
        if (n % i == 0) return false;
    }
    return true;
}

int main() {
    int n;
    cin >> n;
    int sum = 0;
    for (int i = 2; i <= n; i++) {
        if (isprime(i)) sum += i;
    }
    cout << sum << endl;
    return 0;
}