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


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