#include <stdio.h>

FILE *f,*s;

long long int rez;
long int n,i,j,v[1000000];

int main()
{
	f=fopen("fractii.in","r");
	s=fopen("fractii.out","w");
	
	fscanf(f,"%ld",&n);
	
	for(i=1;i<=n;++i)
		v[i]=i;
	
	for(i=2;i<=n;i++)
	{
		if(v[i]==i)
		{
			for(j=i;j<=n;j+=i)
			{
				v[j]=v[j]/i*(i-1);
			}	
		}	
	}	
	
	for(i=1;i<=n;i++)
		rez+=v[i];
	
	rez=rez*2-1;
	
	fprintf(s,"%lld",rez);
	
	fclose(s);
	
	return 0;
}