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

void testcase() {
    int p,d,m,s;
    cin>>p>>d>>m>>s;
    int ans=0;
    while (s>=p) {
        s-=p;
        ans++;
        //cout<<ans<<' '<<s<<' '<<p<<endl;
        if (p>m) {
            p=max(p-d, m);
        }
    }
    cout<<ans<<endl;
}

int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    testcase();
    return 0;
}