#include <cstdio>
#include <cstring>
#include <algorithm>
using namespace std;

//calculates phi(p^k), for p prime and k > 0
int phi_prime(int p, int k) {
	if (p == 1) {
		return 1;
	}
	int answer = 1;
	for (int i = 0; i < k - 1; i++) {
		answer *= p;
	}
	answer *= (p - 1);
	return answer;
}

int N;
bool read() {
	if (scanf("%d", &N) == EOF) {
		return false;
	}
	return true;
}

void process() {
	int answer = 1;
	for (int i = 2; i <= N / i; i++) {
		bool divides = false;
		int power = 0;

		while (N % i == 0) {
			divides = true;
			power++;
			N /= i;
		}

		if (divides) {
			answer *= phi_prime(i, power);
		}
	}
	if (N > 1) {
		answer *= phi_prime(N, 1);
	}
	printf("%d\n", answer / 2);
}

int main() {
	while (read()) {
		process();
	}
	return 0;
}