#include<bits/stdc++.h>
using namespace std;
#define ll long long int
#define pb push_back
int main()
{
    ios_base::sync_with_stdio(0),cin.tie(0),cout.tie(0);
     ll p,s,d,c=0,m,cost,cur;
     cin>>p>>d>>m>>s;
     cost=p;
     cur=p;
     vector<ll>v;
     v.pb(cost);
     while(cur<200000)
     {
         cost-=d; cost=max(m,cost);
         ll last=v.size()-1;
         cur=v[last]+cost;
         v.pb(cur);
     }
     c=upper_bound(v.begin(),v.end(),s)-v.begin();
     cout<<c;
}