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