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


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int p,d,m,s;
    cin>>p>>d>>m>>s;
    int count=0,cost=0;
    if(p<s)
    {
         cost+=p;
        count++;
    }
    else if(p==s)
    {
        cout<<"1";
        return 0;
    }
   else {
       cout<<"0";
       return 0;
   }
    int temp=p;
    while(cost<=s)
    {
       
        temp-=d;
         if(temp<=m)
        break;
          cost+=temp;
            count++;
       
          
      
        
     
    }
    while(cost<=s)
    {
      
         
        cost+=m;
         count++;
       
        
    }
    cout<<--count;
    return 0;
}