#include <iostream>
using namespace std;

int main() {int p,d,m,s,i,j,c=0; 
cin>>p>>d>>m>>s;
for(i=p;i>m;i-=d)
{
    s-=i;
    if(s>=0) c++;
    else break ;
}
if(s>0) c+=s/m;
cout<<c;
    return 0;
}