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


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