def distance(x,y,x1,y1):
	m = (x-x1)**2 + (y-y1)**2
	return (m**0.5)

def moves(r,x,y,x1,y1):
	d = distance(x,y,x1,y1)
	m = d/(2*r)
	if(m == int(m)):
		return int(m)
	else:
		return int(m)+1

r,x,y,x1,y1 = map(int,input().split())
print(moves(r,x,y,x1,y1))