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

        }
        else{
            p=m;
        }
        count++;
    } 
    cout<<count-1;
    return 0;
}