#include <bits/stdc++.h>

using namespace std;

int howManyGames(int p, int d, int m, int s) {
    int count=0;
    int c=p;
    while(s>0){
        s=s-c;
        c=c-d;
        if(m>c)
            c=m;
        count++;
    }
    if(s==0)
    return count;
    else return count-1;
}

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;
}