#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
    // m = min game price
    // p = starting game price
    // d = successive reduction of each game price
    vector<int> priceList;
    int currentPrice = p;
    
    while (currentPrice > m){
        priceList.push_back(currentPrice);
        if (currentPrice - d < m)
            currentPrice = m;
        else
            currentPrice -= d;
    }
    priceList.push_back(m);
    int count = 0;
    int totalCost = 0;
    int costIndex = 0;
    while (totalCost < s) {
        currentPrice = costIndex < priceList.size()-1 ? priceList[costIndex++] : priceList[costIndex];
        if (totalCost+currentPrice > s) break;
        totalCost += currentPrice;
        count++;
    }
    return count;
}

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;
}