#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s) {
    // Return the number of games you can buy
    int games = 0;
    bool ok = false;
    while(p >= m) {
        if(p > s) {
            ok = true;
            break;
        }
        games ++;
        s -= p;
        p -= d;
    }
    if(!ok) {
    while(s >= m) {
        s -= m;
        games ++;
    }
    }
    return games;
}

int main() {
    int p;
    int d;
    int m;
    int s;
    cin >> p >> d >> m >> s;
    int answer = howManyGames(p, d, m, s);
    cout << answer << endl;
    return 0;
}