#include <stdio.h>
#include <stdlib.h>

double power(double x, int n)
{
	double value, result;

	printf("call power(%lf, %d) \n", x, n);
	if (n == 0) {
		printf("return 1\n");
		return 1;
	}
	else if ((n % 2) == 0) {
		value = power(x*x, n / 2);
		printf("return %lf \n", value);
		return value;
	}
	else {
		value = power(x*x, (n - 1) / 2);
		result = x * value;
		printf("return %lf * %lf \n", x, value);
		return result;
	}
}

int main(void)
{
	double  x, value_slow, value;
	int n;

	x = 2;
	n = 10;

	value = power(x, n);

	printf("power(%lf, %d) = %lf \n", x, n, value);
}