#include <math.h>
#include <stdio.h>

unsigned int isNatural(double num)
{
	return ((num >= 0) && (0.0 == fmod(num, 1.0)));
}

int main()
{
	double num;

	scanf("%lf", &num);
	printf("%s\n", isNatural(num) ? "Natural" : "Unnatural");

	return 0;
}