#include <stdio.h>
long prim[500000];
long prim1[10000];
long n,i,j,l;
bool b;
int main()
    {
    freopen("fractii.in","r",stdin);
    freopen("fractii.out","w",stdout);
    scanf("%ld",&n);
    i=2;
    while(i<=n/2)
      {
      while((i<=n/2)||(prim[i]))i++;
      for(j=2*i;j+i<=n/2;j+=i) prim[j]=1;
      }
    j=1;
    for(i=1;i<=n/2;i++)
      if(!prim[i])
        {
        prim1[j]=i;j++;
        }
    l=n*n-(n-1);
    for(i=2;i<=(j-1);i++) 
      {
      l-=(n/prim1[i])*(n/prim1[i]-1);
      }
    printf("%ld\n",l);
    return 0;
    }