#include <stdio.h>
int a[1000001];
 
long long calculare(int n,int a[1000001]){
	long long nr=0,i,j;
	 
	for (i=2;i<=n;i++)
		a[i]=i;
	a[1]=0;
 
	for (i=2;i<=n;i++){
		if (a[i]==i)
	for (j=i;j<=n;j+=i)
		a[j]-=a[j]/i;
		nr+=a[i];
	}
 
 
	return 2*nr+1;
}
int main()
{
	FILE* f=fopen("fractii.in","r");
	FILE* g=fopen("fractii.out", "w");
	int n;
	 
	fscanf(f,"%d", &n);
	fprintf(g,"%lld",calculare(n,a));
	 
	fclose(f);
	fclose(g);
	return 0;
}