#include<cstdio>
#include<cmath>
#include<iostream>
#include<algorithm>
using namespace std;

const double zero=1e-12;

int p,q,a,n;
int sol;

void dfs(int start,double sum,int cura,int left){
	if(sum<-1*zero)return;
	if(sum<=zero&&sum>=-1*zero){
		sol++;
		return;
	}else{
		int i,j;
		
		for(i=start;left*(double)1/i>=sum-zero&&i*cura<=a+zero;i++){

			dfs(i,sum-(double)1/i,i*cura,left-1);
		}
	}
}
int main(){
	while(1){
		scanf("%d%d%d%d",&p,&q,&a,&n);
		if(p==0&&q==0)break;
		sol=0;
		dfs(1,(double)p/q,1,n);
		printf("%d\n",sol);
	}
}