import math

aux = input().split(" ")
r = int(aux[0])
x1 = int(aux[1])
y1 = int(aux[2])
x2 = int(aux[3])
y2 = int(aux[4])

dist = math.sqrt(math.pow(y2 - y1, 2) + math.pow(x2 - x1, 2))
ans = math.ceil(dist / r / 2)
print(ans)
 	 	 	 	            									 	