#include <bits/stdc++.h>
using namespace std;

#define fast ios::sync_with_stdio(false);cin.tie(0); cout.tie(0)

typedef long long ll;
const ll inf = (ll)1e14;
const ll N = (ll)2e5;

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