#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 p;
    int d;
    int m;
    int s;
    cin>>p>>d>>m>>s;
    int c=0;
    if(p<m)
        p=m;
    s=s-p;
    while(s>=0)
    {
        c++;
        p=p-d;
        if(p<=m)
            p=m;
        s=s-p;
    }
    cout<<c;
}