#include<iostream.h>
#include<fstream.h>
long long int v[1000001], i, j, n, s;
ifstream f("fractii.in");
ofstream g("fractii.out");
int main(){
	f>>n;
	for(i=2;i<=n;i++)
		v[i]=i-1;
	for(i=2;i<=n;i++){
		s+=v[i];
		for(j=i*2;j<=n;j+=i)
			v[j]-=v[i];
	}
	g<<s*2+1;
	return 0;
}