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


int main() {
    int p, d, m, s;
    int c=0, sum=0;
    cin>>p>>d>>m>>s;
    while(p>=m && sum<=s){
        sum=sum+p;
        p=p-d;
        c++;
    }
    
    if(sum>s){
        cout<<c-1<<endl;
    }
    
    else{
        while(sum<=s){
            c++; 
            sum=sum+m;
        }
        cout<<c-1<<endl;
    }
        
    
    return 0;
}