#include<iostream>
#include<algorithm>
#include<vector>
#include<string>
#include<queue>
using namespace std;

#define sz(x) (int)(x.size())
#define fr(i,a,b) for(int i=a;i<b;++i)
#define fdr(i,a,b) for(int i=b-1;i>=a;--i)
#define mp make_pair
#define pb push_back
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
/////////////////


void solve(){
	int p, d, m, s;
	cin >> p >> d >> m >> s;
	int ans = 0;
	while(s >= p){
		s -= p;
		++ans;
		p -= d;
		p = max(p, m);
	}

	cout << ans << endl;
}

int main(){
#ifdef _DEBUG
	freopen("input.txt","r",stdin);
	freopen("output.txt","w",stdout);
#endif

	solve();

	return 0;
}