#include <bits/stdc++.h>

using namespace std;

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

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;
}