#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s) {
    int c = 0;
    while(true){
        if(s - p >= 0){
            s -= p;
            c++;
            p -= d;
            if(p < m)
                p = m;
        }else{
            break;
        }
    }
    return c;
}

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;
}