#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 c=0,k=0;
    while(k<=s&&p>=m){
        k=k+p;
         p=p-d;
        c++;
    }
    if(k==s) return c;
    if(k>s) return c-1;
    while(k<=s){
        k=k+m;
        c++;
    }
    if(k==s) return c;
    if(k>s) return c-1;
    return 0;
}

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;
}