#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 m,p,d,s,count=0;
    cin>>m>>p>>d>>s;
    while(s>=m)
    {
        if(m>d && count!=0)
            m=m-p;
        if(m<d)
            m=d;
        s=s-m;
        count++;
    }
    cout<<count;
    return 0;
}