#include <bits/stdc++.h>
using namespace std;

int main(){
    int a, b, c, d;
    cin >> a >> b >> c >> d;
    int ans = 0;
    while(a > 0 && b >= c){
        if(ans + 1 + c > d){
            break;
        }else{
            ans++;
            a--;
            b -= c;
        }
    }

    cout << ans << endl;

    return 0;
}