#include <stdio.h>
#include <stdlib.h>
int E[1000000];
int main()
{
    FILE *dinuin,*dinuout;
    dinuin=fopen("fractii.in","r");
    dinuout=fopen("fractii.out","w");
    int i,n,j,s=1;
    fscanf(dinuin,"%d",&n);
    for(i=2;i<=n;i++)
        E[i]=i;
    for(i=2;i<=n;i++)
        if(E[i]==i)
            for(j=i;j<=n;j=j+i)
                E[j]=E[j]/i*(i-1);
    for(i=2;i<=n;i++)
        s=s+2*E[i];
    fprintf(dinuout,"%d",s);

    return 0;
}