#include <iostream>
#include <stdio.h>
#include <vector>
#include <string>
#include <math.h>
#include <algorithm>
#include <map>
#include <set>

#define sz(x) ((int)x.size())
#define all(x) (x).begin(), (x).end()
#define pb(x) push_back(x)
#define mp(x, y) make_pair(x, y)

typedef long long int64;

using namespace std;


int howManyGames(int p, int d, int m, int s) {
    int ans = 0;
    int price = p;
    while (s >= price) {
        s -= price;
        price = max(price - d, m);
        ++ans;
    }
    return ans;
}

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;
}