#include<cstdio>
#define maxn 1000010
FILE *f, *g;
long long a[maxn],i,j,n,k;

int main()
{
	f=fopen("fractii.in","r");
	g=fopen("fractii.out","w");
	
	fscanf(f, "%d",&n);
	
	for(i=1; 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]=a[j]*(i-1)/i;
	
	for(i=2; i<=n; ++i) k+=a[i]*2;
	
	fprintf(g, "%d\n",++k);
	
	fclose(f);
	fclose(g);	
	return 0;
}