#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=0,cnt=0;
    while(sum+p<=s){
        sum=sum+p;
        //cout<<p<<" "<<sum<<"\n";
        if((p-d)>=m)
            p=p-d;
        else
            p=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;
}