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#include<iostream>
#include<fstream>
using namespace std;
int main () {
ifstream fin("fractii.in");
ofstream fout("fractii.out");
long int n, i, j, nr=0;
fin>>n;
long int v[n];
for (i=1; i<=n; i++)
v[i]=i;
for (i=2; i<=n; i++)
if(v[i]==i)
for(j=i; j<=n; j+=i)
v[j]=v[j]/i*(i-1);
for (i=1; i<=n; i++)
nr+=2*v[i];
fout<<nr-1;
return 0;
}