#include<stdio.h>

#define M 1000001

FILE *fin=fopen("fractii.in", "r");
FILE *fout=fopen("fractii.out", "w");
long long n,i,j,nr;
float v[M];

int main()
{
	fscanf(fin, "%d", &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]/=i;
				v[j]*=(i-1);
			}
	for (i=1; i<=n; i++)
		nr+=v[i];
	fprintf(fout,"%lld", 2*nr-1);
	fclose(fin);
	fclose(fout);
	return 0;
}