#include <bits/stdc++.h>
#define ll long long
using namespace std;

int visit[1002][1002];
long a[1002][1002];
string gr[1002];
int n,m;

int main()
{
    
   long p,d,m,s;
   cin>>p>>d>>m>>s;
   long currprice = p,items = 0;
   while(1){
    if(currprice <= m || s <= 0) break;
    else{
        s-=currprice;
        currprice-=d;
        if(s >= 0) items++;
    }    
   }
   if(s >= currprice){
        items+=(s/m);
    }
    cout<<items<<endl;

   return 0;
}