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


int main() {
    int p,d,m,s;
    cin>>p>>d>>m>>s;
    int c=0;
    while(s && s>=m){
        if(s-p>=0) {s=s-p; c++;}
        else break;
        if(p-d>m) p=p-d;
        else p=m;
    }
    cout<<c;
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    return 0;
}