#include <iostream>
#include <fstream>

using namespace std;
int cmmdc(int x, int y)
{
	r = x % y;
	while (r)
	{
		x = y;
		y = r;
		r = x % y;
	}
	return y;
}
int main()
{
	int v, i, j, s = 0;
	ifstream f("fractii.in");
	ofstream g("fractii.out");
	f >> v;
	for (i = 1; i < v / 2; i++)
		for (j = 1; j < v; i++)
			if (cmmdc(i, j) == 1)s = s + 2;
	s = s - 1;
	if (v % 2 == 1)
	{
		for (j = 1; j < v; i++)
			if (cmmdc(v / 2 + 1, j) == 1)s = s + 1;
	}
	g << s;
	f.close();
	g.close();
}