#include <cstdio>
#include "stdlib.h"

int main()
{
	int *phi;
	FILE *f = fopen("fractii.in","r");
	FILE *g = fopen("fractii.out","w");

	int n;
	fscanf(f,"%d",&n);

	phi = (int*)malloc((1+n)*sizeof(int));
	long long s = 1;

	//compute phi(n)
	for (int i = 1; i <= n; ++i)
		phi[i] = i-1;
	for (int i = 2; i <= n; ++i)
	{
		 for (int j = 2*i; j <= n; j += i)
			phi[j] -= phi[i];
		 s += 2*phi[i];
	}

	fprintf(g,"%lld",s);

	fclose(f);
	fclose(g);
}