#include <stdio.h>
int No[1000000];
	
int main ()
{
	FILE *in, *out;
	in=fopen("fractii.in", "r");
	out=fopen("fractii.out", "w");
	long n, i, j, k, NrPrime=0, TOT;
	scanf("%ld", &n);
	No[1]=1;
	for(i=2; i<=n; i++)
	{
		TOT=i;
		for(j=2*i; j<=n; j+=i)
			No[j]=1;
		for(k=2; k<=i; k++)
			if(!No[k]&&i%k==0)
				TOT*=(k-1), TOT/=k;

		NrPrime+=TOT;
	}
	printf("%ld\n", NrPrime*2+1);
	fclose(in);
	fclose(out);
	return 0;
}