import math

def distancia(x0,y0, x1,y1):
	
	d = math.sqrt(((x0-x1)**2) + ((y0-y1)**2))
	
	return d

r, x0, y0, x1, y1 = map(int, raw_input().split())

v =  distancia(x0,y0,x1,y1)/(2*r)

if v%1 != 0:
	
	v = int(v) + 1
	
else:
	v = int(v)
	
print v