#include<cstdio>

using namespace std;

long long taumeitauz[1000002],s;
int i,n,j;

int main()
{
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    scanf("%d",&n);
    for(i=2;i<=n;i++)
    {
        taumeitauz[i]=i;
    }
    for(i=2;i<=n;i++)
    {
        if(taumeitauz[i]==i)
        {
            for(j=2;j<=n;j+=i)
            {
                taumeitauz[j]/=i;
                taumeitauz[j]*=(i-1);
            }
        }
    }
    for(i=2;i<=n;i++)
    {
        s+=taumeitauz[i];
    }
    printf("%lld\n",2*s+1);
}