#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 */
    long long int p,d,m,s;
    cin>>p>>d>>m>>s;
    long long int sum=0;
    long long int comeon=0;
    while(1)
    {
        sum=sum+p;
        p=p-d;
        if(p<=m){p=m;}
        if(sum<=s){comeon++;}
        if(sum>s){break;}
    }
    cout<<comeon<<endl;
  
    
    
   
    return 0;
}