// 2004‘“ΰ—\‘IC Unit Fraction Partition

#include <iostream>
#include <cmath>

using namespace std;

const double EPS = 1e-12;

int p, q, a, n, c;
double d;

void solve(int s, int t, double sum, int m){
	if(m==n) return;
	for(int i=s;;i++){
		if(t*i>a) break;
		if(abs(d - (sum + 1.0/i)) < EPS) c++;
		if(d - (sum + 1.0/i) > EPS) solve(i,i*t,sum+1.0/i,m+1);
	}
}

int main(){
	while(cin >> p >> q >> a >> n){
		if(!p) break;
		d = (double)p/q;
		c = 0;
		solve(1,1,0.0,0);
		cout << c << endl;
	}
}