#include<iostream>
#include<algorithm>
#include<math.h>
#include<string>
#include<cstring>
#include<iomanip>
#include<stdio.h>
#include<limits>
#include<map>
#include<set>
#include<list>
#include<vector>
#include<stack>
#define gcd __gcd
#define pb(x) push_back(x)
#define ll long long
#define in(x) scanf("%d",&x)
#define mod 1000000007
#define sz(x) x.size()
#define pii pair<ll,ll>
#define mst(x,a) memset(x,a,sizeof(x))
#define F first
#define S second
#define m_p make_pair
#define sortv(v) sort(v.begin(),v.end())
#define rsortv(v) sort(v.rbegin(),v.rend())
using namespace std;

int main()
{
    ios::sync_with_stdio(0);
    int a,d,m,s;
    cin>>a>>d>>m>>s;
    int ans=0;
    while(1)
    {
        if(s<a)
            break;
        s-=a;
        ans++;
        if(a-d>=m)
            a-=d;
        else
            a=m;


    }
    cout<<ans;

    return 0;
}