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