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


int main() {
    int initial_price, subsequent_diff,min_value,wallet_cash;
    cin >> initial_price >> subsequent_diff >> min_value >> wallet_cash;
    int current_sum = 0;
    int price_item = initial_price;
    int count = 0;
    while(wallet_cash > current_sum){
        if(price_item > min_value){
            current_sum += price_item;
            if(current_sum > wallet_cash)
                break;
            price_item = price_item-subsequent_diff;
        }
        else{
            current_sum += min_value;
            if(current_sum > wallet_cash)
                break;
        }
        count++;
    }
    cout << count;
    return 0;
}