#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s) {
    // Return the number of games you can buy
    int sum,c,tp;
    sum=p;
    tp=s;
    c=5;
    while((s>=m) && (tp<=s))
    {
        sum=p-d;
       
        tp=tp+s;
        c=c+1;
        
    }
    return c;
}

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;
}