#include <cstdio>
#include <vector>
using namespace std;
FILE *f=fopen("fractii.in","r");
FILE *g=fopen("fractii.out","w");
int phi[1000005];
int N;
long long nr;
int main()
{
    fscanf(f,"%d",&N);
    for(int i=1;i<=N;i++)
        phi[i]=i;
    for(int i=2;i<=N;i++)
    {
        if(phi[i]==i)
        {
            for(int j=i;j<=N;j+=i)
                phi[j]=phi[j]/i*(i-1);
        }
        nr+=phi[i];
    }
    nr=nr*2+1;
    fprintf(g,"%lld",nr);
    return 0;
}