#include <iostream>
using namespace std;


int main() {
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    ios_base::sync_with_stdio(false);
    int p,d,m,s;
    cin>>p>>d>>m>>s;
    int t=0;
    while(s>=p){
           t+=1;
           s-=p;
           if(p-d>m)
               p-=d;
           else
               p=m; 
    }
    cout<<t;
    return 0;
}