#include<bits/stdc++.h>
using namespace std;
int main()
{
 long long int p,d,m,s,co=0,res=0;
 cin>>p>>d>>m>>s;

for(;;)
{
    if ((res+p)<=s)
    {
        if ((p-d)>=m)
        {
            res+=p;
            p=p-d;
        }
        else
            res+=m;
        co++;

    }

    else
        break;
}
cout<<co<<endl;
    return 0;
}