#include <cstdio>
#include <cmath>
#include <iostream>
using namespace std;
#define LL long long

int n;
int p,d,m,s;

int main(){
	scanf("%d%d%d%d",&p,&d,&m,&s);
	
	int res = 0;
	int cost = p;
	while ( cost <= s ){
		res++;
		s -= cost;
		cost = max( cost - d, m );
	}
	
	cout << res << endl;
	
	return 0;
}