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


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