#include<stdio.h>
#include<math.h>
#include<stdlib.h>
int main(){
long int n,s=1,i,j,*phi;
FILE *f=fopen("fractii.in","r"),*g=fopen("fractii.out","w");
fscanf(f,"%ld",&n);
phi=malloc(n*sizeof(long int));
for(i=1;i<=n;i++)
phi[i]=i-1;
for(i=2;i<=n;i++){
    j=2*i;
    while(j<=n)
    {
        phi[j]-=phi[i];
        j=j+i;
    }
    s+=2*phi[i];
}
fprintf(g,"%ld",s);
fclose(f);
fclose(g);
return 0;
       }