#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 sum=0,count=0;
    while(sum<=s){
        sum+=p;
        if((p-d)>m)
             p=p-d;
        else
            p=m;
       count++;
    }
    cout<<count-1;
    return 0;
}