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


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