#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,tsum,count;
    sum=p;
    tsum=p;
    count=1;
    while((sum>=m)&&(tsum<=s))
    {
        sum=sum-d;
        tsum=tsum+sum;
        count=count+1;
    }
     return count;
}

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;
}