#include <stdio.h>

unsigned long a[1000000];
unsigned long n,ossz;

void tolt(unsigned long x){
 unsigned long temp,i;
 temp=n/x-1;
 i=x;
 while(i<=n){
  a[i]+=temp;
  i+=x;
 }

}

int main(){
unsigned long  i,temp;
freopen("fractii.in","r",stdin);
freopen("fractii.out","w",stdout);
scanf("%ld",&n);

for(i=3;i<=n/2;i++){
 if((i%2==1)&&(a[i]==0)){
  tolt(i);
 }
}
ossz=0;  temp=n/2-1;

for(i=2;i<=n;i++){
 if(i%2==0){
  ossz+=(n-temp-1-a[i]);
 }else{
  ossz+=(n-a[i]-1);
 }

}
ossz+=n;

printf("%ld\n",ossz);

 return 0;
}