#include <iostream>

using namespace std;

struct frac_t
{
	int x, y;

	// constructors
	frac_t(void) {
	}
	frac_t(int a, int b = 1) {
		x = a; y = b;
		int r;
		while((r = a % b) != 0) { a = b; b = r; }
		x /= b; y /= b;
	}
};

frac_t operator -(const frac_t &a, const frac_t &b)
{
	return frac_t(a.x * b.y - a.y * b.x, a.y * b.y);
}

bool operator <(const frac_t &a, const frac_t &b)
{
	return a.x * b.y < a.y * b.x;
}

bool operator ==(const frac_t &a, const frac_t &b)
{
	return a.x == b.x && a.y == b.y;
}

int count(frac_t pq, int a_min, int a_max, int n)
{
	if(n == 0) return 0;

	int c = 0;
	for(int i = a_min; i <= a_max; i++) {
		frac_t u(1, i);

		if(u < pq)
			c += count(pq - u, i, a_max / i, n - 1);
		else if(u == pq)
			++c;
	}

	return c;
}

int main(void)
{
	int p, q, a, n;
	while(cin >> p >> q >> a >> n) {
		if(p == 0 && q == 0 && a == 0 && n == 0) break;
		cout << count(frac_t(p, q), 1, a, n) << endl;
	}

	return 0;
}