import math

data = input()

r = int(data[:data.find(" ")])
data = data[data.find(" ")+1:]
x1 = int(data[:data.find(" ")])
data = data[data.find(" ")+1:]
y1 = int(data[:data.find(" ")])
data = data[data.find(" ")+1:]
x2 = int(data[:data.find(" ")])
data = data[data.find(" ")+1:]
y2 = int(data)

dx = abs(x2-x1)
dy = abs(y2-y1)
moving = math.pow(dx,2) + math.pow(dy,2)
moving = math.sqrt(moving)
steps = moving/(2*r)

if (steps%1 != 0):
	steps = int(steps)+1

print(int(steps))