#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    int p, d, m, s;
    cin>>p>>d>>m>>s;
    int ans = 0;
    int now = p;
    while (s >= now) {
        s -= now;
        ans++;
        now -= d;
        if (now <= m) now = m;
    }
    cout<<ans;
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    return 0;
}