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


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int q,w,e,r;
    cin>>q>>w>>e>>r;
    int curr_price = q;
    int ans = 0;
    while(r>0){
        r-=curr_price;
        ans++;
        curr_price -=w;
        if(curr_price<e){
            curr_price = e;
        }
        if(r<0){
            ans--;
            break;
        }
    }
    cout<<ans;
    return 0;
}