#include <fstream>
 using namespace std;ifstream in("fractii.in");ofstream out("fractii.out");int v[10000001];int main(){int n,i,j;long long sol=0;in>>n;for(i=2;i<=n;i++){v[i]=i-1;}for(i=2;i<=n;i++){sol+=v[i];for(j=i*2;j<=n;j+=i){v[j]-=v[i];}}out<<sol*2+1;return 0;}