import sys,math
from itertools import groupby
sys.setrecursionlimit(1000000000)
lines = []
for Line in sys.stdin:
  lines.append(Line.rstrip('\n'))


# lines=["4 5 6 5 6"]


r,x,y,x1,y1=list(map(int,lines[0].split()))
del(lines[0])

d=math.sqrt(((x1-x)**2)+((y1-y)**2))
#print(d,2)
m=d/(r*2)
if (m>round(m)):
	print(round(m+1))
else:
	print(round(m))