#include <bits/stdc++.h>

using namespace std;

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