#include <bits/stdc++.h>

using namespace std;
ifstream f("fractii.in");
ofstream g("fractii.out");
int i,j,n,a[1000010];
long long ans;
int main()
{
    f>>n;
    for(i=2;i<=n;i++)
        a[i]=i;
    for(i=2;i<=n;i++)
    {
        if(a[i]==i)
            for(j=i;j<=n;j+=i)
                a[j]=(a[j]/i)*(i-1);
        ans+=2*a[i];
    }
    g<<ans+1;
    return 0;
}