#include <bits/stdc++.h>

using namespace std;



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