#include <fstream>
#include <iostream>
using namespace std;
ifstream inFile("fractii.in");
ofstream outFile("fractii.out");
long int v[1000005];
int main()
{long int n,i,k;
long long int s=0;
inFile >> n;
for(i = 1; i <= n/2; i++)
{
k=2;
v[i]=v[i]+i-1;
while (k*i<=n){
v[i*k]=v[i*k]-v[i];
k++;
}
s=s+v[i];
}for (i==n/2+1;i<=n;i++)
s=s+v[i]+i-1;
s=s*2+1;
outFile << s;
}