#include<fstream>
using namespace std;
fstream f("fractii.in", ios::in), g("fractii.out", ios::out);
long long rez = 0,  n, v[1000000];
int main(void)
{
//07.
f>>n;
//08.
long long i,j;
//09.
for(i=1; i<=n; ++i)
//10.
v[i] = i;
//11.
for(i=2; i<=n; ++i)
//12.
if(v[i]==i)
for(j=i; j<=n; j=j+i )
//14.
v[j]=v[j]/i*(i-1);
//15.
for(i=1; i<=n; ++i)
//16.
rez += v[i];
//17.
g << rez*2 - 1 << '\n';
//18.
f.close();
g.close();
return 0;
}