#include <fstream>

using namespace std;

#define dim 1000000

long v[dim];

int main()
{
	long i, j, n, s=0;
	
	ifstream fin("fractii.in");
	ofstream fout("fractii.out");
	
	fin>>n;
	int f=0;
	for(i=2;i<=n;++i)
	{
		
		if(v[i]==0)
		{
			for(j=i+i;j<=n;j+=i)
			{
				if(v[j]==0)
				v[j]=j-j/i;
				else
					v[j]=v[j]-v[j]/i;
			}
		
		s+=i-1;
		}
		else
			s+=v[i];
			
			
			
	}
	fout<<2*s+1;
	return 0;
}