#include<cstdio>
FILE *in,*out;
int v[1000001],n,i,j;
long long s;
int main()
{
	in=fopen("fractii.in","r");
	fscanf(in,"%d",&n);
	fclose(in);
	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*(i-1);
	for(i=1;i<=n;i++)s+=v[i];
	out=fopen("fractii.out","w");
	fprintf(out,"%I64d",s+s-1);
	fclose(out);
}