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

int p,d,m,s;
int main() {
   cin>>p>>d>>m>>s;
    int count=0;
    int to=0,c;
    int a,b;
    a = p;
    for(int i =p;i>=m;i-=d)
    {
        to += i;
        if(to > s)
            break;
        count++;
    }
    if(to < s)
    {
        while(to < s)
        {
            to += m;
            if(to > s)
                break;
            count++;
        }
    }
    cout<<count<<endl;
}