#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s) {
    // Return the number of games you can buy
    int cnt = 0;
    
    while (s >= 0) {
        if (s >= p) {
            s -= p;
        }
        else break;
        //cout << s << " " << p << "\n";
        
        cnt ++;
        p = max(p - d , m);
    }
    return cnt;
}

int main() {
    int p;
    int d;
    int m;
    int s;
    cin >> p >> d >> m >> s;
    int answer = howManyGames(p, d, m, s);
    cout << answer << endl;
    return 0;
}