#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s) {
    
    int sum=0;
    int x=0;
    
    while(sum<=s)
    {
        if(p<=m)
        {
            p=m;
        }
        sum+=p;
        p=p-d;
        x++;    
    }
    
    return x-1;
}

int main() {
    int p;
    int d;
    int m;
    int s;
    cin >> p >> d >> m >> s;
    int answer = howManyGames(p, d, m, s);
    cout << answer << endl;
    return 0;
}