kook = raw_input();
import math

r = int(kook.split()[0])
x = int(kook.split()[1])
y = int(kook.split()[2])
xprime = int(kook.split()[3])
yprime = int(kook.split()[4])

dist = math.sqrt( (yprime-y)**2 + (xprime-x)**2 )

itor = 1

if x == xprime and y == yprime:
	print 0
elif dist - r == itor*2*r:
	print 1
else:
	while dist - r > itor*2*r:
		itor += 1
	print itor + 1
