#include <iostream>
using namespace std;
int p,d,m,s, nr=0, cost;
int main()
{
    cin>>p>>d>>m>>s;
    cost=p;

    while(cost<= s)
    {
        nr++;
        s-=cost;
        if(cost-d>= m) cost=cost-d;
        else cost=m;
    }
    cout<<nr;
    return 0;
}