#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
  ios::sync_with_stdio(false);
	int p, d, m, s;
	cin >> p >> d >> m >> s;
	int r=0;
	int i = 0;
	while (s >= r)
	{
		r = r + p;
		if (p - d < m) { p = m; }
		else { p = p - d; }
		i++;
	}
	cout << i-1;
    return 0;
}