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

int main()
{
    int p,d,m,s,res,count=1;
    cin>>p>>d>>m>>s;
    s = s-p;  res = p-d;  
    while(s>0)
    {
        
        if(res <= m)
        {
            res = m;
            s = s-res;
            count++;
        }
        else
        {
            s = s-res;
            count++;
            res = res-d;
        }
    }
    if(s==0)
        cout<<count;
    else
        cout<<count-1;
    return 0;
}