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


int main() {
    int p,m,d,s;
    cin>>p>>d>>m>>s;
    int count=0;
    int sum=0;
    while(p>=m&&sum+p<=s)
    {   
        sum=sum+p;
        p=p-d;
        count++;
    }
    //cout<<count<<endl;
    while(sum+m<=s&&p<m)
    {
        sum=sum+m;
        count++;
    }
        cout<<count<<endl;
}