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


int main() {
    
    int p, d, m, s;
    cin >> p >> d >> m >> s;
    
    int q = 0;
    while (s) {
        
        if (s >= p) {
            
            s-=p;
            q++;
            
            p-=d;
            if (p < m)
                p = m;           
            
        }
        else
            break;
        
        
    }
    
    
    cout << q <<  endl;
    
    
    
    return 0;
}