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


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