#include<bits/stdc++.h>
#define ll          long long
#define pb          push_back
#define mp          make_pair
#define f           first
#define s           second
#define pii         pair<int,int>
#define vll          vector<ll>
#define all(a)      (a).begin(),(a).end()
#define sz(x)       (int)x.size()
#define hell        1000000007
#define lbnd        lower_bound
#define ubnd        upper_bound
#define bs          binary_search
#define ios        	ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
using namespace std;
ll i,j,k,l,n,h=25,x,y,m,a[100005];
int main()
{
    ios
    ll p,d,s;
    cin>>p>>d>>m>>s;ll ans=0;
    while(s>=0)
    {
        if(s-p>=0) s-=p,ans++;
        else break;
        p=max(p-d,m);
        //cout<<s<<" "<<ans<<" "<<p<<endl;
    }
    cout<<ans<<endl;
	return 0;
}