#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 next_cost = p;
    
    int games = 0;
    
    while(true)
    {
        s -= next_cost;
        
        if(s < 0)
            break;
        
        games++;
        
        next_cost -= d;
        
        if(next_cost < m)
            next_cost = m;
        
    }
    
    
    return games;
}

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;
}