#include<bits/stdc++.h>

using namespace std;

ifstream f("fractii.in");
ofstream g("fractii.out");

int a[1000005],n;

void rez(int n)
{
    int i, j;
    for(i = 2; i <= n; i++)
        a[i] = i - 1;
    for(i = 2; i <= n; i++)
        for(j = i + i; j <= n; j += i)
            a[j] -= a[i];
}

int main()
{
    int i;
    long long sum=1;
    rez(1000000);
    f >> n;
    for(i = 2; i <= n; i++)
        sum += 2 * a[i];
    g << sum<<"\n";
    return 0;
}