#include <bits/stdc++.h>
using namespace std;
int main() 
{
    int p;
    int d;
    int m;
    long long int s,answer=0;
    cin >> p >> d >> m >> s;
    while(s>0)
    {
        if(( p>=m && s<p) || (p<m && s<m))
        {
            s=0;
            break;
        }
        if(p>=m)
        {
            s-=p;
            p=p-d;
        }
        else
        s-=m;    
        answer++;
    }
    cout<<answer<<endl;
    return 0;
}