#include <bits/stdc++.h>

using namespace std;

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

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;
}