#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s)
{
    long long int cost = p;
    int count = 0, price = p;
    bool flag = false;
    while(cost <= s)
    {
        if(count == 0)
        {
            count++;
        }
        else
        {
            price -= d;
            if(price < m)
                price = m;
            if(cost+price <= s)
            {
                cost += price;
                count++;
            }
            else
                return 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;
}