#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 how_many = 0;
    for ( int price = p; price <= s; ) {
        
        how_many++;
        s = s - price;
        price = (price - d ) > m ? (price - d) : m;
    }
    
    return how_many;
}

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;
}