POJ 1284 Primitive Roots

#include <iostream>
#include <cstdlib>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
using namespace std;

typedef long long LL;

LL n;

LL euler_phi(LL n)
{
	LL m = (int)sqrt(n + 0.5);
	LL ans = n;
	for(LL i = 2; i <= m; i++) if(n % i == 0)
	{
		ans = ans / i * (i-1);
		while(n % i == 0) n /= i;
	}
	if(n > 1) ans = ans / n * (n-1);
	return ans;
}

/*LL euler_phi(LL n)
{
	LL m = (int)sqrt(n + 0.5);
	LL ans = n;
	for(LL i = 2; i <= m; i++) if(n % i == 0)
	{
		ans = ans - ans/i;
		while(n % i == 0) n /= i;
	}
	if(n > 1) ans = ans - ans / n;
	return ans;
}*/

void solve()
{
	LL ans = euler_phi(n-1);
	printf("%lld\n", ans);
}

int main()
{
	while(~scanf("%lld", &n))
	{
		solve();
	}
	return 0;
}