#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 */ 
    long long int p,d,m,s,total=0,count=0;
    cin >> p >> d >> m >> s;
    while(p>m&&total<=s)
    {
        total=total+p;
        p=p-d;
        count++;
    }
    while(total<=s)
    {
        p=m;
        total=total+p;
        count++;
    }
    if(count==0)
        cout<<count;
    else
        cout<<count-1;
    return 0;
}