//let's do it
 #include <iostream>
#include<bits/stdc++.h>
using namespace std;
#define ll long long int
#define inf 1000000000000
#define mod 1000000007
#define pb push_back
#define mp make_pair
#define all(v) v.begin(),v.end()
#define S second
#define F first
#define boost1 ios::sync_with_stdio(false);
#define boost2 cin.tie(0);
#define mem(a,val) memset(a,val,sizeof a)
#define endl "\n"
#define maxn 100001

ll a[maxn];

int main()
{
	boost1;boost2;
	ll i,j,n,x,y,f=0,ans=0,p,d,m,s,cost;
	char ch;
	//string s;
	cin>>p>>d>>m>>s;
	if(p>s)
	{
		cout<<"0";
		return 0;
	}
	ans=1;
	s=s-p;
	cost=p-d;
	while(1)
	{
		if(s<=0)
		break;
		if(cost>s)
		break;
		if(cost<=m)
		{
			f=1;
			cost=m;
		}
		if(cost>s)
		break;
		ans++;
		s-=cost;
		if(f)
		continue;
		cost=cost-d;
	}
	cout<<ans;
	return 0;
}