#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;long int sum=0;int c=0;
    for(int i=p;i>=m;i-=d)
    {
        sum=sum+i;
        if(sum>s)
        {
          sum=0;  
         break;}
        else
            c++;
    }
    if(sum==0)
    { cout<<c<<endl;
    
    }
    else
    {
        c+=(s-sum)/m;
        cout<<c<<endl;
    }    
    return 0;
}