#include <bits/stdc++.h>

using namespace std;

#define ff first
#define ss second
#define _N 100005
#define mk make_pair

const long long inf = 1e18;
const long long mod = 1e9+7;

typedef long long ll;

ll power (ll x, ll y, ll z) { ll c = 1ll; while (y > 0) { if (y % 2) c = (c * x) % z; y /= 2; x = (x * x) % z; } return c; }

const int RIGHT = (1 << 19);

const int N = 300005;

int n;

int main () {

//	freopen ("IN.txt", "r", stdin);

	int p, d, m, s, def = 0;

	scanf ("%d%d%d%d", &p, &d, &m, &s);

	while (0 < s) {
		if (p <= m) p = m;
		s -= p;
		if (s >= 0) def ++;
		p -= d;
	}
	
	printf ("%d", def);

	return 0;
}