#include <bits/stdc++.h>

using namespace std;
ifstream fin ("fractii.in");
ofstream fout ("fractii.out");
long long phi[1000005],i,j,n,cnt;
int main()
{
    fin>>n;
    phi[0]=phi[1]=1;
    for (i=2;i<=n;i++) phi[i]=i;
    for (i=2;i<=n;i++)
        {
            cnt+=phi[i];
            if (phi[i]==i)
                {
                    for (j=i+i;j<=n;j+=i)
                        phi[j]-=(phi[j]/i);
                    phi[i]--;
                    cnt--;
                }
        }
    //for (i=1;i<=n;i++) cout<<phi[i]<<" ";
    fout<<cnt*2+1;
    return 0;
}