#include <fstream>
using namespace std;
ifstream cin("fractii.in");
ofstream cout("fractii.out");
#define MAXN 1000000
int e[MAXN+1];
int main() {int n, i, j;cin>>n;for(i=1; i<=n; i++)e[i]=i;for(i=2; i<=n; i++)if(e[i]==i)for(j=i; j<=n; j+=i)e[j]=e[j]/i*(i-1); long long ans=0; for(i=1; i<=n; i++) ans+=e[i]; cout<<2*ans-1;}