#include <fstream>
using namespace std;
bool v[10000001];
int main()
{
	ifstream f("fractii.in");
	ofstream o("fractii.out");
	int n,i,k,nr;
	f>>n;
	nr=2*n-1;
	for (k=3;k<=n;k++)
	{
		for (i=2;i<=k;i++)
			v[i]=1;
		int last=2;
		for (i=2;i<=k/last;i++)
			if (k%i==0 && v[i]) {for (int s=i;s<k;s+=i) v[s]=0;last=i;}
		for (i=2;i<k;i++) if (v[i]) nr+=2;
	}    
	o<<nr;
	return 0;
}