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


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