#include<bits/stdc++.h>
#include<stdio.h>
using namespace std;
typedef long long ll;
ll ans,p,d,s,m,c,flag;
vector<ll>v;
//map<ll,ll>m;
//string s;
int main()
{
    cin>>p>>d>>m>>s;
    c=p;
    if (p<=s)
    {
        ans++;
        s-=p;
    }
    else
    {
        cout<<"0";
        return 0;
    }
    c=p-d;
    while(1)
    {
        if (s<c)
        {
            break;
        }
        if (c<=m)
        {
            c=m;
            flag=1;
            break;
        }
        ans++;
        s-=c;
        c-=d;
    }
    if (flag==1)
    {
        while(1)
        {
            if (s<m)
            {
                break;
            }
            ans++;
            s-=m;
        }
    }
    cout<<ans;
    return 0;
}