#include <bits/stdc++.h>

using namespace std;

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