#include <algorithm>
#include <bitset>
#include <cmath>
#include <iostream>
#include <queue>
#include <stack>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <vector>

using namespace std;


/***** Generic Code *****/


/* Generic declarations  */

constexpr bool debug = false;
constexpr float EPSILON = 1E-6;
constexpr long long MOD = 1000000007;
constexpr long long MAX_LONG = 9223372036854775807;

typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> vi;

#define dbg(message) if (debug) cout << message
#define getArray(v, n) for (int i = 0; i < n; ++i) cin >> v[i];

/* Generic Functions  */

template <typename T>
void printVector(const vector<T>& v) {
	for (int i = 0 ; i < v.size() ; ++i)
		cout << v[i] << " ";
	cout << '\n';
}

string join(const vector<string>& v, const string& delim) {
	string s = v[0];
	for (int i = 1; i < v.size(); ++i) {
		s += delim + v[i];
	}
	return s;
}

/***** Custom Code *****/


/* Custom Classes */

/* Custom Variables  */


/* Custom Functions  */

int main() {
	ios_base::sync_with_stdio(false);
	cin.tie(0);

	int d, m, p, s;
	cin >> p >> d >> m >> s;

	int games = 0;
	while (s >= p) {
		s -= p;
		p -= d;
		if (p < m) p = m;
		++games;
	}

	cout << games;

	return 0;
}