#include<stdio.h>
long long n;
void descompun()
{
	float p=n;
	for (int i=2; i*i<=n; ++i)
	{
		int ok=0;
		while (n%i==0)
		{
		n/=i;ok=1;
		}
		if (ok)
		p*=(float)(i-1)/i;

	}
	if (n>1)
	p*=(float)(n-1)/n;
	int n=p;
	printf("%d",n);
}
void citire()
{
	freopen("ciur.in","r",stdin);
	freopen("ciur.out","w",stdout);
	scanf("%lld",&n);
	descompun();
}

int  main()
{
	citire();
	return 0;
}