#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s) {
    int n=0;
    while((s-p) >= 0 && p >= m) {
        
            s -= p;
            if(p-d >= m) {
            p -= d;
            } else {
                p = m;
            }
        
        n++;
    }
    
    
    return n;
    // Return the number of games you can buy
}

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;
}