#include <bits/stdc++.h>

using namespace std;


int main() {
    long int p;
    long int d;
    long int m;
    long int s;
    cin >> p >> d >> m >> s;
    long int count=1,sum=p;
    
    for(sum=p;sum<=s;)
    {
        if((p-d)>m)
        {
            p=p-d;
            sum=sum+p;
            count++;
            
        }
       
        else{
            sum=sum+m;
            count++;
            
        }
    }
    cout << count-1;
    return 0;
}