#include<bits/stdc++.h>
using namespace std;

#define ll long long
#define pb push_back
#define mp make_pair
#define pii pair<  int , int >
#define vii vector< int >
#define ff first
#define ss second
#define rep(i,n) for(int i=0;i<n;i++)
#define frep(i , a , b) for(int i = a;i <= b;i++)
#define fast cin.sync_with_stdio(0);cin.tie(0);
#define test int t;cin >> t;while(t--)
#define FI freopen ("in.txt", "r", stdin)
#define FO freopen ("out.txt", "w", stdout)
#define mod 1000000007

int main()
{


            long int i,j,k,m,n,s=0,g=0,z=0,p,d;

            cin>>p>>d>>m>>n;
            vii a;
            while(n>0)
            {
                s=s+p;
                n=n-p;
                if(n<0)
                    break;
                k=p-d;
                if(k<=m)
                {
                  p=m;
                }
                else
                    p=p-d;
                z++;
               // cout<<p<<endl;
            }
           // cout<<s<<endl;
            cout<<z<<endl;



    return 0;
}