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

int main()
{
	long int d, h1, h2, h3;
	long int cnt;

	cin >> d >> h1 >> h2 >> h3;

	if (h2 >= h1&&h2 <= h3 || h2<=h1&&h2>=h1){
		if (h2 < d){
			cout << -1 << endl;
			return 0;
		}
		if (h3 - h2 >= h2 - h1){
			cnt = floor((h2 - h1) / d) +1;
		}
		else if (h3 - h2 < h2 - h1){
			cnt = floor((h3 - h2) / d) +1;
		}
	}
	else{
		cnt = 0;
	}

	cout << cnt << endl;

	return 0;
}