#include <bits/stdc++.h>

using namespace std;

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

int n;
int a[1000005];

int main()
{
    for(int i= 1; i <=1000000; ++i)a[i]=i;
    for(int i = 2; i <= 1000000; ++i)
    {
        if(a[i]==i)
        {
            a[i]--;
            for(int j = i *2; j <= 1000000; j += i)
            {
                a[j]-=a[j]/i;
            }
        }
    }
    fin>>n;
    long long s=0;
    for(int i = 2;i <= n; ++i)
    {
        s+=1LL*a[i];
    }
    fout<<s*2+1;
    return 0;
}