#include <bits/stdc++.h>
#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 */ 
    
    long long p,d,m,s;
    cin>>p>>d>>m>>s;
    long long count=0;
    bool flag=1;
    long long price=0;
    while(true)
    {
        if(flag)
        {
            price=p;
            flag=0;
        }
        else if(p-d>m)
        {
            p=p-d;
            price+=p;
        }
        else price+=m;
       // cout<<price<<" ";
        if(s>=price) count++;
        else break;
    }
    cout<<count;
    return 0;
}