#include<iostream>
#include<fstream>
#include<vector>

using namespace std;

int n;
vector<int> fi;


int main()
{int i,j;
ifstream f("fractii.in",ios::in);
ofstream g("fractii.out",ios::out);

f>>n;

fi.resize(n+1,0);

for(i=1;i<=n;i++)
fi[i]=i;

for(i=2;i<=n;i++)
	if(fi[i]==i)
		for(j=i;j<=n;j+=i)
{fi[j]/=i;
fi[j] *= (i-1);}			

int s=0;
for(i=1;i<=n;i++)
s+=fi[i];
s=s*2;
s--;
g<<s;
g<<endl;

f.close();
g.close();
return 0;
}