#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 cost = p;
    int count = 0;
    int total = 0;
    
    while (s > 0){
       // cout << s << " " << cost << " " << count << endl;
        if (s >= cost){
            count++;
            s -= cost;
        }
        else{
            break;
        }
        if (cost > m){
            cost -= d;
        }
        if (cost <= m){
            cost = m;
        }
    }
    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;
}