#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s) {
    int sum=0,co=0;
    while(sum<=s){
        if(sum+p>s)break;
        else {//cout<<p<<"p ";
            co++;sum+=p;}
        if(p-d>=m)p=p-d;
        else p=m;
        
    }
    return co;
}

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;
}