#include <cmath>
#include <cstdio>
#include <vector>
#include <iostream>
#include <algorithm>
using namespace std;


int main() {
    int p,d,m,s,exp,cost;
  cin>>p>>d>>m>>s;
  int count=0;
  cost=p;
  exp=0;
  while(s>exp)
  {
  	count++;
  	exp+=cost;
  	if(cost-d>=m)
  	cost=cost-d;
  	else
  	cost=m;
  }
  if(s==exp)
  cout<<count<<"\n";
  else
  cout<<count-1<<"\n";
    /* Enter your code here. Read input from STDIN. Print output to STDOUT */   
    return 0;
}