import math

a = raw_input()

tokens = a.split();

r = int(tokens[0])

x = int(tokens[1])

y = int(tokens[2])

xx = int(tokens[3])

yy = int(tokens[4])

distance = math.sqrt(abs(x-xx)**2 + abs(y-yy)**2)

print int(math.ceil(distance/(r*2)))
