#include <bits/stdc++.h>

using namespace std;

const double eps = 1e-10;

int n, m;
int ans;
double need;

void dfs(int st, double now, int last) {
    if(now - need > eps) return ;
    if(st == n) {
        if(fabs(now - need) < eps) ++ans;
        return ;
    }
    for(int i = last + 1; i <= m; i++) {
        dfs(st + 1, now + 1.0 / i, i);
    }
}

int main() {
    int x, y;
    cin >> n >> m >> x >> y;
    need = 1.0 * x / y;
    dfs(0, 0.0, 0);
    cout << ans << endl;
    return 0;
}