#include <bits/stdc++.h>

using namespace std;

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

int main() {
    int p; //initial prize
    int d; // Step down prize
    int m; // Min prize
    int s; //Money in your wallet
    cin >> p >> d >> m >> s;
    int answer = howManyGames(p, d, m, s);
    cout << answer << endl;
    return 0;
}