#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,c,ans,st;
    cin>>p>>d>>m>>s;
    c=0,ans=0,st=p;
    while(true){
        if(c+st<=s){
            ans++;
            c=c+st;
            st=st-d;
            if(st<m)
                st=m;
        }
        else
            break;
    }
    cout<<ans;
    return 0;
}