#include<bits/stdc++.h>
#define fi first
#define se second
#define mp make_pair
#define pb push_back
#define pob pop_back
#define pf push_front
#define pof pop_front
#define FOR(i,n) for(int i=0;i<n;i++)
#define REPP(i,l,r,c) for(int i=l;i<=r;i+=c)
#define REP(i,l,r) REPP(i,l,r,1)
#define FORD(i,n) for(int i=n-1;i>=0;i--)
#define REVV(i,l,r,c) for(int i=max(l,r),_m=min(l,r);i>=_m;i-=c)
#define REV(i,l,r) REVV(i,l,r,1)
using namespace std;

typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> vi;
typedef pair<int,int> pii;
typedef pair<ll,ll> pll;
typedef vector<pii> vii;

const int INF=(int)2e9;
const double EPS=(double)1e-9;
const double PI=(double)acos(-1.0);
const ll MOD=(ll)1e9+7;

int irand(int lo, int hi){
	return (((double)rand())/(RAND_MAX+1.0)) * (hi-lo+1) + lo;
}

string toString(ll x) {
	stringstream ss;
	ss << x;
	return ss.str();
}

ll toNumber(string S) {
	ll ret;
	sscanf(S.c_str(),"%lld",&ret);
	return ret;
}

void syncOff(){
	ios_base::sync_with_stdio(0);
	cin.tie(0);
}


int main(){
	syncOff();
	int p,m,d,s;
	cin>>p>>d>>m>>s;
	int now=p;
	int cnt=0;
	while(s>=now){
		cnt++;
		s-=now;
		now = max(now-d,m);
//		cout<<now<<endl;
	}
	cout<<cnt<<endl;
	return 0;
}