#include <stdio.h>
long a[1000002],i,j,n;
long long k;
FILE *f,*g;
int main()
{
	f=fopen("fractii.in","r");
	g=fopen("fractii.out","w");
	fscanf(f,"%ld",&n);
	k=2;
	for(i=2;i<=n;i++){a[i]=i;}
	for(i=2;i<=n;i++){
		if(a[i]==i){for(j=i;j<=n;j+=i){a[j]/=i;a[j]*=(i-1);}}
		k+=2*a[i];
	                 }
	k--;
	fprintf(g,"%lld",k);
return 0;
}