#include <fstream>

using namespace std;

ifstream fin ("fractii.in");
ofstream fout("fractii.out");

int n,fi[1000010],i,j;
long long s;


int main()
{
    fin >> n;
    //fi[1]=1;
    for (i=2;i<=n;++i)
    {
        fi[i]+=i-1;
        s+=fi[i]*2;

        for (j=i+i;j<=n;j+=i)
        {
            fi[j]-=fi[i];
        }
    }
    fout <<s+1;

    return 0;
}