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


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