#include <stdio.h>
#include <stdlib.h>

int main(void)
{
	long long i,j,n,k,v[1000001];
	FILE *f,*g;
	f=fopen("fractii.in","r");
	g=fopen("fractii.out","w");
	k=0;
	fscanf(f,"%lld",&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;
				v[j] = v[j]*(i-1);
			}
		k=k+v[i];
	}
	fprintf(g,"%lld",(2*k+1));
	fclose(f);
	fclose(g);
	return 0;
}