#include <fstream>

using namespace std;

#define infile "ciur.in"
#define outfile "ciur.out"

int main (void)
{
	ifstream in(infile);
	int n,j,phi[100],i;
	in>>n;
	for (i=1;i<=n;i++) 
		phi[i]=i;
	for (i=2;i<=n;i++)
		if (phi[i]==i)
			for (j=i;j<=n;j+=i) 
				phi[j]/=i, phi[j] *= (i-1);
	ofstream out(outfile);
	out<<phi[n];
	in.close();
	out.close();
	return 0;
}