#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

const ll mod = 998244353;
const int N = 20210926;
const int SB = 32;

vector<int> lp(N+1), pr;

void prep(){
    for (int i=2; i <= N; ++i) {
        if (lp[i] == 0) {
            lp[i] = i;
            pr.push_back(i);
        }      

        for (int j = 0; i * pr[j] <= N; ++j) {
            lp[i * pr[j]] = pr[j];
            if (pr[j] == lp[i]) {
                break;
            }
        }
    }
}

int main(){
    prep();

    int n;
    cin >> n;

    ll ans = 0;

    //for(int i = 1; i <= n; i++){
     //   ans += pref[i] - pref[i-1];
    //}

    cout << ans << "\n";
}