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