import math
s=input().split(' ')
s=[int(i) for i in s]
r=s[0]
x=s[1]
y=s[2]
x2=s[3]
y2=s[4]
d=2*r

t=math.sqrt(((x2-x)*(x2-x))+((y2-y)*(y2-y)))

t1=t/d

if t1 != int(t1):
        t1=int(t1)+1
else:
        t1=int(t1)
print(t1)