#include <bits/stdc++.h>

using namespace std;

ifstream fin("fractii.in");
ofstream fout("fractii.out");

int v[1000005];

int main()
{
    int N;
    fin >> N;
    for(int i = 2; i <= N; ++ i){
        v[i] = i - 1;
    }
    for(int i = 2; i <= N; ++ i){
        if(v[i] == i - 1){
            int cnt = 1;
            for(int j = i + i; j <= N; j += i){
                v[j] -= cnt;
                ++ cnt;
            }
        }
    }
    int s = 0;
    for(int i = 2; i <= N; ++ i){
        s += v[i];
    }
    fout << 2 * s + 1 << '\n';
    return 0;
}