#include<fstream>
using namespace std;
ifstream cin("fractii.in");
ofstream cout("fractii.out");
int N,i=2,j,s[1000001];
long long r;
int main()
{
    cin>>N;
    for(;i<=N;i++)s[i]=i-1;
    for(i=2;i<=N;i++)
    {
        r+=s[i];
        for(j=2*i;j<=N;j+=i)s[j]-=s[i];
    }
    cout<<2*r+1;
}