#include <stdio.h>
#include <stdlib.h>
#include <math.h>

int main() {

	int d = 0;

	long int left = 0;
	long int center = 0;
	long int right = 0;

	char str[20];
	long int count = 0;

	gets(str);
	d = atoi(str);
	gets(str);
	left = atoi(str);
	gets(str);
	center = atoi(str);
	gets(str);
	right = atoi(str);

	if(!((center < left && center < right) || (center > left && center > right))){

		long int lc = left - center;
		long int rc = right - center;

		if(lc > 0){
			long double l = double(abs(lc)) / d;
			long double r = double(abs(rc)) / d;
			if(l > r)
				count = ceil(l) + 1;
			else
				count = ceil(r) + 1;

		} else {
			long double l = double(abs(lc)) / d;
			long double r = double(abs(rc)) / d;
			if (l > r)
				count = ceil(r) + 1;
			else
				count = ceil(l) + 1;


		}

	}
	else if((left == 0 && center == 0) || (right == 0 && center == 0))
		count = -1;


	printf("%ld",count);

	return 0;

}