#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s) {
    int sum=0,k=0;
    if (s<p) return 0;
    while (sum<=s) {
        if (p>m) { sum+=p; p-=d; }
        else if (p<=m){ p=m;  sum+=m; }
        k++;
    }
    return k-1;
    // Return the number of games you can buy
}

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;
}