#include <iostream>

using namespace std;

int gcd( int m, int n ) {
	return ( n == 0 )? m : gcd(n, m%n);
}


int P, Q, A, N;	

void recursive( int nterm, int denomLbound, int num, int denom, int denomProduct, int &result ) {
	if ( nterm == N ) return;

	for ( int d = denomLbound; d <= A; d++ ) {
		if ( denomProduct * d > A ) break;

		const int newDenomProduct = denomProduct * d;
		const int GCD = gcd(denom, d);
		const int newDenom = denom*(d/GCD);
		const int newNum = num*(d/GCD) + (denom/GCD);

		const int numUpperBound = num*(d/GCD) + (N-nterm)*(denom/GCD);
		if ( P*newDenom > Q*numUpperBound ) break;

		if ( P*newDenom == Q*newNum )
			result++;
		else if ( P*newDenom < Q*newNum )
			continue;
		else
			recursive(nterm+1, d, newNum, newDenom, newDenomProduct, result);
	}
}

int main() {
	while ( true ) {
		cin >> P >> Q >> A >> N;
		if ( P == 0 && Q == 0 && A == 0 && N == 0 ) break;
	
		int result = 0;
		recursive(0, 1, 0, 1, 1, result);
		cout << result << endl;
	}

	return 0;
}