#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 n = 0;
    int c = p;
    while(s >= c){
        s -= c;
        n++;
        c -= d;
        if(c < m){
            c = m;
        }
    }
    cout<<n<<endl;
    return 0;
}