#include <iostream>
#include <fstream>
using namespace std;
ifstream in("fractii.in");
ofstream out("fractii.out");
int ndv[1000001];
int main()
{
    int n;
    in>>n;
    long long cnt=0;
    for(int i=2;i<=n;i++)
        ndv[i]=i-1;
    for(int i=2;i<=n;i++)
    {
        for(int j=2*i;j<=n;j+=i)
            ndv[j]-=ndv[i];
        cnt+=ndv[i];
    }

    cnt=cnt*2+1;
    out<<cnt;
    return 0;
}