#include <stdio.h>

typedef unsigned int uint;

/* the sequence, 0-th member is 0 */
uint f(uint n)
{
	return n < 2 ? n : (n&1) ? f(n/2) + f(n/2 + 1) : f(n/2);
}

uint gcd(uint a, uint b)
{
	return a ? a < b ? gcd(b%a, a) : gcd(a%b, b) : b;
}

void find(uint from, uint to)
{
	do {
		uint n;
		for (n = 1; f(n) != from ; n++);
		printf("%3u at Stern #%u.\n", from, n);
	} while (++from <= to);
}

int main(void)
{
	uint n;
	for (n = 1; n < 16; n++) printf("%u ", f(n));
	puts("are the first fifteen.");

	find(1, 10);
	find(100, 0);

	for (n = 1; n < 1000 && gcd(f(n), f(n+1)) == 1; n++);
	printf(n == 1000 ? "All GCDs are 1.\n" : "GCD of #%d and #%d is not 1", n, n+1);

	return 0;
}