#include <bits/stdc++.h>
using namespace std;
typedef unsigned long long ull;
typedef long long ll;
#define fastio() ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define test() ull t;cin>>t;while(t--)
#define pb push_back
#define mkp make_pair
#define nl cout<<endl
#define MOD 1000000007
#define loop(i,start,end) for(int i=start;i<end;i++)

int main() 
{
    fastio();
    int p,d,m,s;
    cin>>p>>d>>m>>s;
    int cnt=0,sum=0,cur=p;
    while(1)
    {
        if(s>=cur)
        {
            s-=cur;
            cnt++;
            cur-=d;
            if(cur<=m)
                cur=m;
        }
        else
            break;
    }
    cout<<cnt;
    
  
	return 0;
}