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


int main() {
    int p,d,m,s;
    cin >> p;
    cin >> d;
    cin >> m;
    cin >> s;
    int n=s/m;
    int A[n+1];
    int count=0;
    int sum=0;
    for(int i=0;i<=n;i++)
    {
        if(p>=m)
        {
            A[i]=p;
            p=p-d;
        }
        else
        {
            A[i]=m;
        }
    }
    for(int i=0;i<=n;i++)
    {
        if(sum>s)
        break;
        sum=sum+A[i];count++;
    }
    cout << count-1;
    return 0;
}