#include <iostream>
#include <fstream>
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
const int MAX=100000001;
int fi[MAX],n;
int main()
{
    in>>n;
    for(int i=1; i<=n; ++i)
        fi[i]=i;
    for(int i=2; i<=n; ++i)
        if(fi[i]==i)
            for(int j=1; j<=n; j=j+i)
                fi[j]-=fi[j]/i;
    long long ans=-1;
    for(int i=1; i<=n; ++i)
        ans=ans+2*fi[i];
    out<<ans;
    return 0;
}