# cook your dish here
#n=int(input())
import math
nn=list(map(int,input().rstrip().split()))

dia=2*nn[0]
x=nn[1]
y=nn[2]
xx=nn[3]
yy=nn[4]

dist=math.sqrt((yy-y)*(yy-y)+((xx-x)*(xx-x)))
numm=dist/dia
print(math.ceil(numm))
    