#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    int p,d,m,s;
    cin>>p>>d>>m>>s;
    int cnt = 0;
    int tot = 0;
    while (tot <= s){
        cnt ++ ;
        tot += p;
        if (p - d >= m) p -= d;
        else p = m;
    }
    if (tot > s) cout << cnt - 1;
    return 0;
}