#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s) {
    int sum=p,c=1,pre=p;
    if(pre>s)
        return 0;
    while(sum<s)
    {
        pre=pre-d;
        if(pre<m)
        {
           pre=m;
        }
        sum+=pre;
        if(sum>s)
            break;
        c++;
    }
   
    return c;
    // 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;
}