#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 i=0;
    int count=0;
    while(s>=0){
        s-=max((p-i*d),m);
        if(s>=0){
            count++;
        }
        i++;
    }
    cout<<count;
    return 0;
}