#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 pr , d , m , s ;
    cin >> pr >> d >> m >> s ;
    int cur = pr ;
    int ans = 0 ;
    while ( s - cur >= 0 )
    {
        s -= cur ;
        cur -= d ;
        if ( cur <= m )
        {
            cur = m ;
        }
        ans ++ ;
    }
    cout << ans ;
    return 0;
}