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