import math

r,x,y,x1,y1  = map(int,input().split())

dist =math.sqrt((x-x1)**2 + (y-y1)**2)

if dist != int (dist):
    dist = int (dist)+1  
res = dist//(2*r)
if (dist) % (2*r) != 0 :
    res = res +1
print  ( int(res)) 
