#include <bits/stdc++.h>

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