#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s) {
    int cnt = 0;
    int cst = p;
    for(int i=0;;i++)
    {
        if(cst<m || s<cst){
            if(cst<m)
                cst=m;
            break;
        }
        s-=cst;
        cnt++;
        cst-=d;
    }
    while(s>=cst)
    {
        s-=m;
        cnt++;
    }
    return cnt;
}

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;
}