#include "bits/stdc++.h"
using namespace std;
#define fastcin {\
    cin.tie(0);\
    ios::sync_with_stdio(false);\
}
#define rep(i, a, b) for(int i = a; i < b; i++)
#define print(x) cout << x << "\n"

bool p[1001];
int main() {
    fastcin;
    int n, ans = 0;
    cin >> n;
    rep(i, 2, n+1) {
        if(!p[i]) {
            ans+=i;
            for(int j=i+i; j<n+1; j+=i) p[j] = true;
        }
    }
    print(ans);
    return 0;
}