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