#include<stdio.h>
#define Maxp 1000005
long n,q,b[Maxp],x;
long long s;
FILE *f,*g;

void prim()
{long i,j;
for(i=2;i<=n;i++)
{x=i;
for(j=1;b[j]<=i/2&&j<=q;j++)
if(i%b[j]==0)
{x/=b[j];
x*=b[j]-1;}
if(x==i)
{q++;
x--;
b[q]=i;}
s+=x;}

}

int main()
{f=fopen("fractii.in","r");
g=fopen("fractii.out","w");
fscanf(f,"%ld",&n);
prim();
long i;
fprintf(g,"%lld\n",2*s+1);
fclose(f);
fclose(g);
return 0;}