#include <bits/stdc++.h>
using namespace std;
const int N = 1234567;
const int mod = 1e9+7;
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;
typedef priority_queue<pii, vector<pii>, greater<pii>> min_pq;
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define inf 1e18
int main()
{
	ios_base:: sync_with_stdio(false); cin.tie(0);
	// freopen ("inp","r",stdin);
	// freopen ("out","w",stdout);
	// string s;
	int p,d,m,s,ans;
	cin>>p>>d>>m>>s;
	int cnt=0;
	while(1)
	{
		// cout<<p<<endl;
		if(s-p>=0)
			s-=p;
		else
			break;
		cnt++;
		if(p>=m)
		{
			if(p-d>=m)
				p-=d;
			else
				p=m;
		}
	}
	cout<<cnt<<endl;
	return 0;
}