#include<cstdio>
using namespace std;
int n,i,j;
long long v[1000001],s;
int main ()
{
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    scanf("%d",&n);
    s=0;
    for(i=1;i<=n;i++)
        v[i]=i;
    for(i=2;i<=n;i++)
        if(v[i]==i)
            for(j=i;j<=n;j+=i)
                v[j]=v[j]/i*(i-1);
    for(i=2;i<=n;i++)
        s+=v[i];
    printf("%lld",(2*s)+1);
    return 0;
}