#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int oPrice, salePrice, reduc, money;
    int numGames = 0;
    cin >> oPrice >> reduc >> salePrice >> money;
    
    while (money - oPrice >= 0) {
        ++numGames;
        money -= oPrice;
        if (oPrice > salePrice) {
            oPrice -= reduc;
            oPrice = oPrice < salePrice ? salePrice : oPrice;
        }
    }
    
    cout << numGames << endl;
    
    return 0;
}