import math

def main():
	r, x, y, x1, y1 = map(int, raw_input().split())
	
	d = math.sqrt((x1 - x) ** 2 + (y1 - y) ** 2)
	if d == int(d):
		print int((d / (r * 2)))
	else:
		print int((d / (r * 2))) + 1
	
if __name__ == '__main__':
	main()