#include <fstream>

using namespace std;
ifstream in ("fractii.in");
ofstream out ("fractii.out");
int v[1000002];
int main()
{
    int n,i,j;
    long long ans=1;
    in>>n;
    for (i=2;i<=n;i++)
        v[i]=i-1;
    for (i=2;i<=n;i++)
        for (j=i*2;j<=n;j+=i)
            v[j]-=v[i];
    for (i=2;i<=n;i++)
        ans+=v[i]*2;
    out<<ans;
    return 0;
}