// #define DEBUGGING
#include <bits/stdc++.h>
#define endl '\n'
#define ALL(V) (V).begin(), (V).end()
#define ALLR(V) (V).rbegin(), (V).rend()
using ll = std::int64_t;
using ull = std::uint64_t;
using PLL = std::pair<ll, ll>;
using TLL = std::tuple<ll, ll, ll>;
template <typename T> using V = std::vector<T>;
template <typename T> using VV = V<V<T>>;
template <typename T> const T& var_min(const T &t) { return t; }
template <typename T> const T& var_max(const T &t) { return t; }
template <typename T, typename... Tail> const T& var_min(const T &t, const Tail&... tail) { return std::min(t, var_min(tail...)); }
template <typename T, typename... Tail> const T& var_max(const T &t, const Tail&... tail) { return std::max(t, var_max(tail...)); }
template <typename T, typename... Tail> void chmin(T &t, const Tail&... tail) { t = var_min(t, tail...); }
template <typename T, typename... Tail> void chmax(T &t, const Tail&... tail) { t = var_max(t, tail...); }
template <typename T> const T& clamp(const T &t, const T &low, const T &high) { return std::max(low, std::min(high, t)); }
template <typename T> void chclamp(T &t, const T &low, const T &high) { return t = clamp(t, low, high); }
namespace init__ { struct InitIO { InitIO() { std::cin.tie(nullptr); std::ios_base::sync_with_stdio(false); std::cout << std::fixed << std::setprecision(30); } } init_io; }
#define mv_rec make_v(init, tail...)
template <typename T> T make_v(T init) { return init; }
template <typename T, typename... Tail> auto make_v(T init, size_t s, Tail... tail) { return V<decltype(mv_rec)>(s, mv_rec); }
#undef mv_rec
using namespace std;

#ifdef DEBUGGING
#include "../../debug/debug.cpp"
#else
#define DEBUG(...) 0
#define DEBUG_SEPARATOR_LINE 0
#endif

ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }

PLL add_f(PLL p, PLL q) {
    ll a, b, c, d;
    tie(a, b) = p;
    tie(c, d) = q;
    a *= d;
    c *= b;
    return PLL(a + c, b * d);
}

bool eq(PLL p, PLL q) {
    ll a, b, c, d;
    tie(a, b) = p;
    tie(c, d) = q;
    return a * d == b * c;
}

struct Solver {
    ll p, q, a, n;
    PLL want;

    Solver() {
        cin >> p >> q >> a >> n;
        want = PLL(p, q);
    }
    
    ll calc(ll v, ll rest, PLL cur) {
        if (is_same(cur)) return 1;
        ll ret = 0;
        ll x, y;
        tie(x, y) = cur;
        if (a < y * v) return ret;
        if (is_smaller(add_f(cur, PLL(rest, v)))) return 0;
        for (ll i = 0; i <= rest; i++) {
            if (i) cur = add_f(cur, PLL(1, v));
            if (is_larger(cur)) break;
            if (a < cur.second) break;
            ret += calc(v + 1, rest - i, cur);
        }
        return ret;
    }

    bool solve() {
        if (!(p + q + a + n)) return false;
        {
            ll g = gcd(p, q);
            p /= g;
            q /= g;
        }
        cout << calc(1, n, PLL(0, 1)) << endl;
        return true;
    }

    bool is_smaller(PLL o) {
        ll c, d;
        tie(c, d) = o;
        return c * q < d * p;
    }

    bool is_same(PLL o) {
        ll c, d;
        tie(c, d) = o;
        return c * q == d * p;
    }

    bool is_larger(PLL o) {
        return !(is_smaller(o) || is_same(o));
    }
};

int main() {
    while (Solver().solve());
    return 0;
}



Measured memory_bytes: 3188