from sys import stdin
import math
r,x1,y1,x,y = stdin.readline().strip().split()
r=int(r);x1=int(x1);y1=int(y1);x=int(x);y=int(y)
r=2*r
r=r*r
di = x1-x
di2 = y1-y

di = di*di + di2*di2
ans =(di*1.0)/r
xx = int(math.sqrt(ans))
if xx*xx < ans:
    xx+=1
print xx

