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