#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

// The Largest Integer 18446744073709551615

#define eps 1e-9
#define all(a)   a.begin(),a.end()
#define mp make_pair
#define F first
#define S second
#define pb push_back
#define sz size()
#define rd(inp) scanf("%lld",&inp)
#define rd2(inp1, inp2) scanf("%lld %lld",&inp1, &inp2)
#define rl(inp) scanf("%d",&inp)
#define pf(out) printf("%lld\n", out);

const long long linf = 1e18+5;
const int mod = (int) 1e9 + 7;
const int inf = 1e9;

ll fpow(ll base,ll power){
	ll result = 1;
	while (power > 0){
		if (power%2 == 1) result=(result*base);
  		base = (base*base);
  		power /= 2;
  	}
	return result;
}

int main(){
	ll p, d, m, s;
	cin >> p >> d >> m >> s;
	ll ans = 0;
	while ( s >= 0 ){
		if ( s >= p ){
			s -= p;
		}
		else{
			break;
		}
		p -= d;
		p = max(p, m);
		ans ++;
	}
	cout << ans << endl;
	return 0;	
}