#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int S) {
    int ans  = 0 ;
    int c = 0 ;
    int s = p ;
    while(1){
        if(s < m) s = m ;
        c += s ;
        if(c > S){
            break ;
        }
        ans++ ;
        s = s - d ;
    }
    return ans ;
}

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;
}