#include <bits/stdc++.h>
using namespace std;

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

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;
}