#include<iostream>
#include<fstream>
//susing namespace std;
ifstream fin("fractii.in");
ofstream fout("fractii.out");
int phi(int n)
{int k=2;
int p=n;
int d;
    while(n>1)
    {d=0;
        while(n%k==0)
        {
            n=n/k;d++;
        }

        if(d>0)
            p=(p*(k-1))/k;

        k++;
    }
return p;
}
int main()
{int s=1,n,i;
fin>>n;

for(i=1;i<=n-1;i++)
    s=s+2*phi(i+1);
fout<<s;
return 0;
}