#include<stdio.h>
long long o;
long n,v[1000000];


int main()
{
	FILE *f;
	f=fopen("fractii.in","rt");
	fscanf(f, "%d", &n);
	fclose(f);
	f=fopen("fractii.out","wt");
	for(long i=1;i<=n;i++)
		v[i]=i;  
	for(long i=2;i<=n;i++)
		if(i==v[i])
			for(long j=i;j<=n;j+=i)
				v[j]=v[j]/i*(i-1);
	for(long i=2;i<=n;i++)
		o+=v[i];

	fprintf(f,"%lld", o+o+1);
	fclose(f);
	return 0;
}