import math

l1=[int(x) for x in input().split()]
r=l1[0]
x1=l1[1]
y1=l1[2]
x2=l1[3]
y2=l1[4]
dis=((x2-x1)**2+(y2-y1)**2)
dis=dis**0.5
if(dis==0):
    print('0')
else:
    step=0
    while dis>2*r:
        if(step==0):
            step+=1
            dis-=r
        else:
            step+=1
            dis-=2*r
    print(step+1)
