
import math

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

dia = 2*r;

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

if(dist==0):
    print(0)
else:
    ans = 0
    ans+= dist//dia
    if(dist%dia!=0):
        ans+=1
    print(int(ans))