#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s) {
    int x=0;
    int t=0;
    int cp=p;
    int c=0;
    while(t<=s-cp)
    {
        c++;
        t+=cp;
        //cout<<cp<< " ";
        cp-=d;
        if(cp<=m)
            cp=m;
        
    }
    
    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;
}