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


int main() {
    
    int i,j,k,x,y,z,ans=0;
    int n,p,d,m;
    
    cin>>p>>d>>m>>n;
    
    while(p>m){
        if(n>=p){
            n=n-p;
            p=p-d;
            ans++;
        }else{
            break;
        }
    }
    
    while(p<=m && n>=m){
        ans++;
        n=n-m;
    }
    
    cout<<ans<<endl;
    return 0;
}