import math
t = input().split(" ")
r = int(t[0])
x1 = int(t[1])
y1 = int(t[2])
x2 = int(t[3])
y2 = int(t[4])
dist = ((x1-x2)*(x1-x2))+((y1-y2)*(y1-y2))
dist = math.sqrt(dist)
count=dist//(2*r)
if dist%(2*r)!=0:
 count+=1
print(int(count))