#include <iostream>

using namespace std;

int main()
{
    int p,d,m;
    int money;
    int games{0};
    cin >> p >> d >> m >> money;
//    cout << p << " "<< d << " "<< m << " "<< money << " ";
    while(money >= p){
        money -= p;
        games++;
        if(p>m)
            p = max(p-d,m);
    }
    cout << games;
    return 0;
}