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