#include<fstream>
using namespace std;
long n,i,j,a[1000001];
long long s;
int main()
{ifstream f("fractii.in");
ofstream g("fractii.out");
f>>n;
for(i=1;i<=n;i++) a[i]=i-1;
for(i=2;i<=n;i++) for(j=2;i*j<=n;j++) a[i*j]=a[i*j]-a[i];
s=1;
for(i=1;i<=n;i++) s=s+2*a[i];
g<<s;
return 0;
}