#include<bits/stdc++.h>
#include<vector>

#define pb push_back
#define rep(i, a, n) for(int (i)=a; (i)<(n); (i)++)
#define FOR(i, n) rep(i, 0, n)
#define F(n) FOR(i, n)
#define FF(n) FOR(j, n)
#define repi(i, a, n) for(int (i)=a; (i)<=(n); (i)++)
#define FORI(i, n) repi(i, 1, n)
#define FI(n) FORI(i, n)
#define FFI(n) FORI(j, n)
#define IN(x) cin<<(x);
#define INFO(a) cout<<"info "<<a<<endl
#define vi vector<int>
#define vll vector<ll>
#define pii pair<int, int>
#define vpii vector<pair<int, int> >
#define sortv(x) sort((x).begin(), (x).end())
#define sortvd(x) sort((x).begin(), (x).end(), greater<int>())
#define lboundv(x, v) lower_bound((x).begin(), (x).end(), (v))
#define uboundv(x, v) upper_bound((x).begin(), (x).end(), (v))
#define ite iterator
#define fi first
#define se second
#define mems(a, v) memset((a), (v), sizeof((a)))
#define lmid(l, r) ((l)+(r)-1)/2
#define rmid(l, r) ((l)+(r))/2+1
#define LD long double

typedef long long ll;

using namespace std;

int gcd(int a, int b) {
	if(a>b) swap(a, b);
	if(!a) return b;
	else return gcd(b%a, a);
}

int main() {
	ios::sync_with_stdio(0);
	ll p, d, m, s; int ans=0;
	cin>>p>>d>>m>>s;
	ll cur=p;
	while(s>=0) {
		if(s<cur) break;
		s-=cur;
		ans++;
		cur-=d;
		if(cur<m) cur=m;
	}
	/*while(s-cur>=0 && cur-d>=m) {
		s-=cur;
		cur-=d;
		ans++;
	}
	while(s-m>=0) {
		s-=m;
		ans++;
	}*/
	cout<<ans<<endl;
	return 0;
}