#include<iostream>
using namespace std;


int main() {
   int p,d,m,s;

    cin>>p>>d>>m>>s;

    int x=0,c=0,i;

    for(i=p;i>=m;i=i-d){

        if(c<=s){
        c+=i;
        x++;
        }
    }
while(c<=s){
    c+=m;
    x++;
}


    cout<<x-1;
return 0;
}