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


int N,k,s[1000005];

int main()
{
    ///
    ifstream f("fractii.in");
    ofstream g("fractii.out");

    f >> N;

    for(int i=2; i<=N; i++)
        s[i] = i-1;
    for(int i=2; i<=N; i++) {
        k+=s[i];
        for(int j = i+i; j<=N; j+=i)
            s[j]-=s[i];
    }
    g<<2*k+1;
    f.close();
    g.close();
    ///
    return 0;
}