/* http://www.cnblogs.com/karl07/ */

 #include <cstdlib>

 #include <cstdio>

 #include <cstring>

 #include <cmath>

 #include <algorithm>

 using namespace std;

 #define ll long long

 const int N=1e7+;

 ll phi[N],prime[N];

 int cnt=,n;

 ll ans;

 void PHI(int n){

     phi[]=;

     for (int i=;i<=n;i++){

         if (!phi[i]){

             prime[++cnt]=i;

             for (int j=i;j<=n;j+=i){

                 if (phi[j]==) phi[j]=j;

                 phi[j]=phi[j]/i*(i-);

             }

         }

     }

 }

 int main(){

     scanf("%d",&n);

     PHI(n);

     for (int i=;i<=n;i++) phi[i]+=phi[i-];

     for (int i=;i<=cnt;i++){

         ans+=phi[n/prime[i]]*-;

     }

     printf("%lld\n",ans);

     return ;

 }