#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    int m, p, d ,s;
    cin >> p >> d >> m >> s;
    
    int cnt = 0;
    int cost = p;
     
    s -= p;
    if (s >= 0)
        ++cnt;

    while(1)
    {
        cost -= d;
        if(cost < m)
            cost = m;
        
        s -= cost;
        if(s >= 0)
            cnt++;
        else
            break;
    }
    
    cout << cnt;
    
    return 0;
}