#include <iostream>
#include <cstdio>

using namespace std;

struct ratio
{
  int c, m;
};

int gcd(int a, int b)
{
  int temp;
  while ( a%b!=0 ) {
    temp = b;
    b = a%b;
    a=temp;
  }
  return b;
}

int countans(const ratio &r, int curm, int curmul, int maxmul, int left)
{
  int i, j;
  int ret=0;
  ratio r2;
  
  for ( i=curm ; r.c*i<r.m ; i++ ) ;
  if ( i*curmul>maxmul ) return 0;
  if ( left==1 ) {
    return r.c*i==r.m?1:0;
  }
  
  while ( (long long)i*curmul<=maxmul && r.c*i<=r.m*left ) {
    r2.c = r.c*i-r.m;
    r2.m = r.m*i;
    if ( r2.c==0 ) {
      ret++;
      i++;
      continue;
    }
    j = gcd(r2.c, r2.m);
    r2.c/=j;
    r2.m/=j;
    /*printf("%d/%d-1/%d=%d/%d from%d %d->%d l %d ret=%d\n",
      r.c, r.m, i, r2.c, r2.m, curm, curmul, maxmul, left, ret);*/
    ret += countans(r2, i, curmul*i, maxmul, left-1);
    i++;
  }
  return ret;
}

int main(void)
{
  int p, q, mul, left;
  ratio r;
  while ( scanf("%d%d%d%d", &p, &q, &mul, &left)==4 &&
	  p!=0 ) {
    r.c=p;
    r.m=q;
    printf("%d\n", countans(r, 1, 1, mul, left));
  }
}