#include <fstream>

using namespace std;
ifstream fi("fractii.in");
ofstream fo("fractii.out");
long long n,i,j,s;
int PHI[1000001];
int main()
{
    fi>>n;
    for(i=1;i<=n;i++)
        PHI[i]=i-1;
    PHI[1]=1;
    for(i=2;i<=n;i++)
        for(j=2*i;j<=n;j+=i)
            PHI[j]-=PHI[i];
    for(i=1;i<=n;i++)
        s+=PHI[i];
    fo<<s*2-1;
    fi.close();
    fo.close();
    return 0;
}